Ecohydrological conditions in two catchments in the Gorce Mountains: Jaszcze and Jamne streams – Western Polish Carpathians

Ecohydrology & Hydrobiology 14 (2014) 229–242

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Original Research Article

Ecohydrological conditions in two catchments in the Gorce Mountains: Jaszcze and Jamne streams – Western Polish Carpathians§ Artur Radecki-Pawlik a,*, Anna Bucała b,1, Karol Plesin´ski a, Paweł Ogle˛cki c a

Department of Hydraulic Engineering and Geotechnics, University of Agriculture in Krakow, Al. Mickiewicza 24-28, 30-059 Krako´w, Poland b Department of Geoenvironmental Research, Institute of Geography and Spatial Organization, Polish Academy of Sciences, Ul. S´w. Jana 22, 31-018 Krako´w, Poland c Department of Environmental Engineering, Warsaw University of Life Sciences, ul. Nowoursynowska 159, 02-787 Warszawa, Poland

A R T I C L E I N F O

A B S T R A C T

Article history: Received 17 August 2013 Accepted 11 June 2014 Available online 24 June 2014

The results of the analysis of ecohydrological (hydrobiological and hydrodynamic) parameters of neighboring catchments, the Jaszcze and Jamne streams, located in the Gorce Mountains in Polish Carpathians are presented. Analysis of the abiotic properties of those river channel ecosystems including shear stress, granulometric properties of gravel, water movement numbers as well as biotic parameters calculated using the Polish Biological Monitoring Working Party (BMWP-PL) benthic invertebrate-based index suggested that even though the two small streams valleys are similar in size and geological characteristics, and are nearby, they have different flow conditions which reflect on the hydrobiological status of those rivers. The aim of this article is to compare the parameters we measured in the field to help develop an understanding of the relationships between different processes at the river channel scale to improve sustainable development in the Jaszcze and Jamne stream catchments. This is especially important in light of the river channel regulation works already undertaken there and in light of the EU Water Framework Directive which main aim is to achieve good ecological status of all water bodies by the end of 2015. An assessment of stream conditions done without a detailed description of the hydrobiological and hydrodynamical parameters could lead to serious errors. This paper shows ways to examine the above-mentioned parameters in order to compare and analyze them and hopefully use them for catchment management. ß 2014 European Regional Centre for Ecohydrology of Polish Academy of Sciences. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.

Keywords: Hydrodynamic Benthos BMWP-PL index Mountain stream

1. Introduction §

This paper in its early version was presented at the International Symposium Ecohydrology, Biotechnology and Engineering: Towards Harmony between the Biogoeosphere and Society on the basis of LongTerm Ecosystem Research held in Ło´dz´, 17–19th September 2013. The special issue of the symposium papers was published in Ecohydrology & Hydrobiology, Vol. 14, No. 1, 2014. * Corresponding author. Tel.: +48 12 693136686. E-mail addresses: [email protected] (A. Radecki-Pawlik), [email protected] (A. Bucała), [email protected] (K. Plesin´ski), [email protected] (P. Ogle˛cki). 1 Tel.: +48 12 422 40 85.

At present, Poland is evaluating criteria connected with the improvement of ecological status of all water bodies modified by river engineering works, as required by the European Union’s Water Framework Directive (2000/60/ WE Directive) by the end of 2015. Other types of evaluations of morphological and biological conditions of the streams have been conducted previously. It should be noted that in mountain streams, even those located

http://dx.doi.org/10.1016/j.ecohyd.2014.06.003 1642-3593/ß 2014 European Regional Centre for Ecohydrology of Polish Academy of Sciences. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.

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close to each other within the same physical-geographical unit and under almost identical climate conditions, different hydrodynamic and hydrobiological conditions can occur which influence not only the morphology but also the environmental life in the streams. Also, we need to consider ecohydrology as a separate factor which harmonizes natural systems with river engineering infrastructure with the objective of achieving the sustainability of various processes, ecosystem services and resilience (Zalewski, 2013). This paper presents the results of field measurements, observations and calculations of basic hydrobiological and hydrodynamics parameters done in the two streams, Jaszcze and Jamne, located in neighboring catchments in the Gorce Mountains, in the Polish part of the Carpathian Mountains. It was noted that the channel modifications, mainly bank reinforcement works, are worsening habitat conditions for water organisms and macrobenthos (Bucała et al., 2013), although not in such drastic way as might be expected (also in Kłonowska-Olejnik and Radecki-Pawlik, 2000; Zase˛pa et al., 2006). It is known that maintaining or reconstructing gravel river bars and different channel microforms (such as grain size and woody debris) will improve the ecological status of rivers and is strongly recommended (Wyz˙ga, 2007; Korpak et al., 2008; RadeckiPawlik and Skalski, 2008a,b; Radecki-Pawlik, 2011; Zalewski, 2013; Wyz˙ga et al., 2011, 2012, 2013, 2014). These interstitial spaces between the grains of gravel are important for macrobenthos (Carling et al., 2006; RadeckiPawlik, 2011; Wyz˙ga et al., 2011, 2012, 2013, 2014). Consequently, we took into consideration gravel in both researched streams to look at their role more closely. Finally, the Polish Biological Monitoring Working Party (BMWP-PL) benthic invertebrate-based index, commonly regarded as an indicator of river water quality, and the resulting taxa richness and BMWP-PL index scores were determined in this study. All the above were utilized to provide an assessment of the conditions in the Jamne and Jaszcze streams. To sum up, as well as typical hydromorphological assessment, the results of research and analysis of the investigated ecohydrological parameters were used as part of the hydromorphological and hydrobiological assessment performed according to the guidelines of the EU Water Framework Directive (Radecki-Pawlik, 2011). Those

results also can serve as examples for environmental engineers, geographers and biologists in future studies of the river environment. It has to be pointed out that some of the parameters presented here were analyzed as a pilot study in a paper presented in Polish by Bucała et al. (2013). The main aim of the Polish paper was to present the results to Polish audiences, ranging from the lowest level of rivers authority administrations to senior managers, directing their practical works and keeping the local managers and designers working in line with the Water Framework Directive which requires only hydrodynamics parameters. 2. Description of the studied catchments The Jaszcze and Jamne catchments are located in the Gorce Mountains and are representative of the Western Flysch Carpathian streams (Fig. 1). The elevation differences (400–600 m) in the Jaszcze and Jamne catchments (11.39 km2 and 8.95 km2, respectively) are typical of medium–high mountains. The Jaszcze and Jamne streams (9.3 km and 6.4 km long, respectively), which are tributaries of the Dunajec River (in the upper Vistula River basin), form the main valley network. The Jaszcze stream originates in bogs situated at an elevation of 1160 m a.s.l. on the slopes of Mount Jaworzyna (1250 m a.s.l.) and joins the Ochotnica River at 610 m a.s.l. The Jamne stream flows from a spring (discharging 0.05 l/s) on the slopes of Mount Gorc (1229 m a.s.l.) at an elevation of 1110 m a.s.l. Its junction with the Ochotnica River is at 600 m a.s.l. In the upper sections of the side valleys, water flows periodically and forms a network of ephemeral streams. Maximum discharges are in February, June and July and can reach up to 3.0 m3/s in the Jaszcze stream and up to 6.0 m3/s in the Jamne stream (Bucała et al., 2013). In these upper sections, water flows periodically, forming a network of episodic streams. The length of the permanent watercourses in the Jaszcze catchment is 41.3 km, and the length of the watercourses in the Jamne catchment is 29.0 km, providing densities of watercourses of 3.5 km km2 and 3.2 km km2, respectively (Gerlach and Niemirowski, 1968; Bucała et al., 2013). The most significant channelization and bank protection works were carried out only in the lower and middle courses of the streams (Photo 1), but such measures were considered unnecessary in the upper courses where the streams were already incised in solid, stable rocks (Photo

Fig. 1. Study area.

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231

Photo 1. Regulated stream channel part using concrete retaining wall on the estuary reach of Jaszcze stream – Jaszcze III.

Photo 3. Rocky channel in Jamne downstream part, result of downcutting (incision) – Jamne III.

1). The first documented channelization in the lower course of the Jamne stream was conducted in 1994 and subsequent works were completed in 2001 and 2003. In addition to the hydrotechnical structures constructed in those years, older measures including 1970s-era concrete retaining walls and gabions are found along the length of the stream. Before the regulation, the streams were characterized by numerous gravel bars, which were larger than the ones that currently exist (Niemirowski, 1974). The Jamne stream was braided in its lower section, and the active channel was almost 20 m wide (Photo 2). In the longitudinal profile, the stream channels were regulated, and in cross-section (especially in the Jamne stream), a few braids separated by gravel bars were distinguished (Bucała, 2012). The lower parts of the stream displayed a tendency toward incision and fine deposits were swept away from the interstitial spaces among boulders and coarse gravels (Photo 3). In 2008, 14 concrete structures and six gabions, with a total length of 834 m, were identified in the Jaszcze stream, while 15 concrete structures and 22 gabions, with total length of 899 m, were found in the Jamne stream. In the Jaszcze stream, 6.4% of the right-bank length and 2.5% of the left-bank length was engineered. In the Jamne stream, 7% of the stream length had been reinforced with concrete

revetment walls and gabions on both the right and left banks. As a result of channelization, the channels were shortened, straightened and narrowed. In the case of the Jamne stream, its length along the segment from 700 m to 3640 m from the outlet was reduced by 180 m, and, as a result, the channel gradient increased from 39% in 1954 to 41% in 2004 (Bucała, 2012). In terms of geology, both catchments are located in the range of the Magura Nappe of the Carpathian Flysch. The soils of this region correspond to bedrock which is formed on the Carpatian Flysh. These are mainly skeletal brown soils developed on weathered sandstone. The Jaszcze and Jamne valleys are located in two climatic vertical zones: (1) a temperate cold zone with a mean annual temperature of 4–6 8C and (2) a cold zone of 2–4 8C, above 1100 m a.s.l. (Hess, 1965). Mean annual air temperature decreases from 6 8C at the valley outlet sections to 3 8C at the river sources (Obre˛bska-Starklowa, 1969). Mean annual precipitation in the years 1958–2008 was 841 mm. Both catchments are overgrown with mixed forest (oak, spruce, pine) of the lower mountain zone (between 600–700 m a.s.l. and 1100 m a.s.l.) and the Carpathian spruce forest which occurs at elevations above 1100 m a.s.l. The upper parts of the valleys are within the borders of the Gorce National Park (GNP), formed in 1981. Both catchments differed distinctly in the length of stream, density of cutting by valleys (the Jaszcze catchment 4.26 km km2, the Jamne catchment 5.33 km km2; Gerlach and Niemirowski, 1968), as well as forest cover – the Jaszcze about 77%, and the Jamne about 55% (also in Bucała, 2012; Bucała et al., 2013). According to the results of measurements at the gauged cross-sections located at the mouth of the valley of the Jaszcze and Jamne streams presented by Niemirowski (1974), the Jaszcze stream had higher annual flow values. 3. Methodology

Photo 2. Natural part on the upper reach of Jamne stream: look at the gravel deposits and natural boulders present here – Jamne I.

Field research was conducted in three transverse profiles for both watercourses: upper (I), middle (II) and lower (III) cross-sections of the Jaszcze and Jamne streams.

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Instantaneous velocity was measured with an OTT, Nautilus type C-2000 RS-Sensa current meter. This device made it possible to estimate water velocities in the range from 0.001 m s1 to 10 m s1, which is crucial for measurements of water velocity in the water velocity logarithmic distribution layer and consequently for calculating dynamic velocity as well as shear stress values. Readings were performed at chosen points which were directly above the stream bottom and also in measurement sections that were 1 m from the stream bed along the cross-section. Velocity profiles at particular measurement points were drawn on the basis of these measurements of instantaneous velocities. These measurements were used to calculate mean velocities, dynamic velocities, different kinds of Reynolds numbers (cross-section flow and grain), Froude numbers and finally shear stresses. Shear stress evaluations were made on the basis of the graphs of water velocities taken above the river bed and analyzed after semi-logarithmic transformation by means of the methods described by Carling (1983) and Gordon et al. (2007). From the velocity profile, its dynamic value (Vs in m s1) can be found from the formula (Gordon et al., 2007; Radecki-Pawlik, 2011): a v ¼ 5:75 where a – factor of straight gradient that takes the form of an equation (where x – height above the bottom where velocity measurement was performed; b – equation free term). Calculated values of dynamic velocities (t in N m2) were used to determine forces that act upon the stream bottom such as shear stresses, after the formula:

t ¼ r  ðv Þ2 where r – water density in 1000 kg m3, v* – dynamic velocity in m s1. Different Reynolds numbers (Re, dimensionless) were obtained from the different formulae (mean (av) and maximal (max) for depth in tachometric and grain perpendicular (dm)) dependent on needs:

vav  h y vmax  h Remax ¼ y v  d m Redm ¼ y where vav – average velocity [m s1], vmax – maximum velocity [m s1], v* – dynamic velocity [m s1], h – water depth [m], dm – mean diameter of grains [m], y – kinetic Reav ¼

viscosity coefficient [m2 s]. Next, different Froude numbers (Fr) at average (av) and maximum (max) depths were determined according to the different formulae (mean and maximal in tachometric perpendicular), again dependent on need:

vav

Frav ¼ pffiffiffiffiffiffi gh

vmax

Frmax ¼ pffiffiffiffiffiffi gh

where vav – average velocity [m s1], vmax – maximum velocity [m s1], h – water depth [m], g – gravity [m s2]. The bottom sediments from the gravel bars that occurred on the river beds were also collected using the surface sampling method according to Wolman (1954). For the collected sediments, diameter (dm in mm) was estimated from: dm ¼

X

di  pi 

X

pi

1

where di – diameter of the individual grains [m]; pi – percentile of the individual grains [%]. Then, having granulometric grain size curves, we calculated several dimensionless granulometric parameters, such as: - the Trask’s sorting coefficient (S0): S0 ¼

d75 d25

- Hazen’s sorting coefficient (u): u¼

d60 d10

- Knoroz’s grain-size diversity indicator (e):

e¼

d95 d5

- Kollis’ uniformity indicator (Cd): Cd ¼

d90  d10 d250

where d – diameter of the individual grains [mm] at various percentiles, indicated by the subscript, within the distribution. To understand more about the hydrobiology of both streams we decided to analyze BMWP-PL index. Generally speaking, the Biological Monitoring Working Party (BWMP) index is a procedure for measuring the water quality using macroinvertebrate species as biological indicators. The basic principle of the method is that various taxa have different tolerance to organic pollution. Since almost every taxon (there are some exceptions, taxa with no BMWP values) may be evaluated on the scale from 1 (highest tolerance for pollutants – lowest importance as biological indicators) to 10 (lowest tolerance – highest importance). In the Polish modification of the BMWP index – the so-called BMWP-PL – the values for each family (if more species of one family is found in the sample, they are counted only once) are summed and the total result decides the water class according to the classification of 2004 which is shown in Table 1. To asses the BMWP-PL index, benthic invertebrate samples were collected at the same cross-section as for collecting and measuring hydrodynamic and granulometric data on 14–15 July and 3–4 November 2013, under similar flow conditions (low flow). No flood wave occurred between these surveys and the channel morphology remained the same. Because such surveys are to be conducted repeatedly in the erodible corridor, a repeatable sampling strategy had to be designed for all cross-sections.

A. Radecki-Pawlik et al. / Ecohydrology & Hydrobiology 14 (2014) 229–242 Table 1 Polish BMWP-PL (Biological Monitoring Working Party) index values. Ecological class number

BMWP-PL value

I II III IV V

>100 70–99 40–69 10–39 <10

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basis of these averaged values of the BMWP-PL index, biologically indicated water-quality classes were assigned to each cross-section.

4. Results and discussion 4.1. Jamne stream

Therefore, we collected the same number of invertebrate samples from each cross-section. In each low-flow channel, samples were taken at three locations representing the main, visually identified habitat conditions (i.e. combinations of water depth, flow velocity and substrate type). At each sampling location, invertebrates were collected using a triangular dip net with a 500 mm mesh size, an Ekman grab, a mosquito dipper, and tweezers (for gathering the invertebrates from cobbles) (Wyz˙ga et al., 2013). Attention was paid to keeping the sampled areas and the sampling times similar for all samples. With different substrate types sampled and different collecting methods used, the surveys focused on determining the taxonomic richness and composition of the assemblages, whereas invertebrate abundance was not analyzed. According to a sampling procedure for the BMWP-PL index, a qualitative, kick-net sample must be collected from all major habitat types occurring along a 100-m-long river reach (Kownacki and Soszka, 2004). Next, the collected samples were temporarily stored at approximately 3 8C to minimize animal predation. After transport to a laboratory, the samples were divided into two aliquots, with one being stored at 3 8C and one preserved in 70% ethanol. The invertebrates were identified partly from the unpreserved material within 2–3 days after the sampling and partly from the samples preserved in 70% ethanol. To enable accurate identification of the habitat preferences of the collected invertebrates, all the specimens were identified to the lowest unquestionably identifiable taxonomic level. The taxonomic composition of the invertebrate assemblages collected during particular surveys was used to calculate the BMWP-PL index score and averages of the scores from both surveys were subsequently determined for each cross-section. On the

In the Jamne stream, cross-section I was located approximately 4 km from the Ochotnica River estuary, in the forested upper part of the catchment (when, during the measurement periods, the measured discharge in the channel was Q = 0.9 m3/s at the outlet to the Ochotnica River). Its bed was cut from solid rock and followed a straight course almost along its full length. The width of the channel at the place of measurement was 5.8 m and the height of the bank was 1.4 m. There was a gravel bar on the left bank. At the distance of about 150 m below this crosssection, the right bank of the watercourse was intensely eroded during every flood. In cross-section I of the Jamne stream, highly concentrated flow in the middle of the channel was observed. The highest velocities (V = 0.423– 0.52 m s1) appeared at point no. 2 in thalweg. In the same place, shear stress reached its highest value in the crosssection (t = 1.511 N m2), exceeding significantly the values from the remaining cross-section points (t = 0.044 N m2 and t = 0.014 N m2, at points 2 and 3, respectively). The Reynolds numbers (Re = 45,307–55,653) and Froude numbers (Fr = 0.361–0.444) at point no. 2 testified to turbulent and subcritical movement (Table 2 and Figs. 2 and 3). At points no. 1 and 3, the sediment mean grain diameters were in a similar range (dm = 51–55 mm). However, in the main current, it was dm = 89 mm. Material which occurred at that point was coarser than in the river bank part of the cross-section where the fine fraction was washed out by flowing water. Wash out of pebbles with diameters up to 100 mm gave evidence of available velocities of V = 2–3 m s1 during mean floods, in accordance with the measurements performed by Niemirowski (1974) (Table 3 and Fig. 2). The second cross-section (II) was approximately 2.1 km from the Ochotnica River estuary, in the middle part of the Jamne valley where the stream bed was not forested.

Table 2 Hydrodynamic parameters of Jamne stream. Cross section

No point

Hmax

vav

I

II

III

1 2 3 1 2 3 4 1 2 3

0.1 0.14 0.03 0.13 0.13 0.14 0.06 0.03 0.17 0.2

vmax

v*

[m s1]

[m] 0.13 0.423 0.127 0.167 0.072 0.199 0.127 0.111 0.211 0.301

0.216 0.52 0.146 0.207 0.095 0.262 0.167 0.14 0.272 0.368

t

Reav

[N m2] 0.007 0.039 0.004 0.007 0.003 0.01 0.007 0.011 0.013 0.012

0.044 1.511 0.014 0.053 0.007 0.105 0.042 0.129 0.167 0.138

Remax

Redm

Frav

[–] 9938 45,307 2905 16,563 7122 21,334 5835 2128 27,400 46,072

16,512 55,653 3348 20,572 9441 28,041 7660 2676 35,349 56,265

Frmax [–]

260 2648 156 350 186 947 396 663 1303 1181

0.131 0.361 0.233 0.148 0.063 0.17 0.166 0.225 0.163 0.215

0.218 0.444 0.269 0.183 0.084 0.224 0.218 0.283 0.211 0.263

Explanations: Hmax – maximum water depth at the measurement points [m], vav – mean velocity [m s1], vmax – maximum velocity [m s1], v* – dynamic velocity [m s1], t – shear stress [N m2], Reav – mean Reynolds number [–], Remax – maximum Reynolds number [–], Redm – grain Reynolds number [–], Frav – mean Froude number [–], Frmax – maximum Froude number [–].

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Fig. 2. Velocities, water depth at the measurement points and the mean diameter of bed materials at the Jamne stream.

There, the bed was cut into solid rock and its stream course was straight. The right bank of the stream was regulated and reinforced with an approximately 68 m long concrete revetment wall (the height of the revetment wall was 2.65 m). However, the left bank was not reinforced and was only 0.8 m high. The stream bed was covered with a gravel bar on the right bank. Upstream of the studied crosssection, the stream course was slightly meandering. Cross-section II was situated in the middle of the stream. The stream there was wider and deeper than in the

previous cross-section. Water depths here were H = 0.13– 0.14 m and only on the left bank (point 4) was H = 0.06 m. Water velocities were in the range of V = 0.127– 0.199 m s1. Only at point 2 was velocity lower (V = 0.072–0.095 m s1) than at the other points. Shear stresses were in range of t = 0.007–0.105 N m2, the Reynolds number was within the range of Re = 5835– 28,041 and the Froude number values were from Fr = 0.063 to Fr = 0.224. All those numbers showed turbulence and subcritical movement (compare Table 2). Mean grain

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SUBCRITICAL TURBULENT MOVEMENT

1

Re = 2000

Water depth - h [m]

0.1

Re = 500

SUPERCRITICAL TURBULENT MOVEMENT

0.01 SUBCRITICAL LAMINAR MOVEMENT

TRANSITION MOVEMENT

0.001

Fr = 1 0.0001 0.001

SUPERCRITICAL LAMINAR MOVEMENT 0.1

10

Average velocity - Vav [m · s-1] JAMNE I

JAMNE II

JAMNE III

JASZCZE I

JASZCZE II

JASZCZE III

Fig. 3. The motion of water of sediment movement in investigated streams.

diameter was dm = 63–91 mm; only at point no. 3 was its value higher (dm = 121 mm). This variation might be due to the higher velocities noticed here, V = 0.199 m s1, where fine particles were washed out from the river bed (Tables 2 and 3 and Figs. 2 and 3). The third cross-section (III) was located in the lower part of valley (approximately 350 m from the Ochotnica River estuary), where the Jamne stream cut into solid rock, with numerous rocky thresholds and outcrops. The width of the channel at the place of measurement was 7.1 m

Table 3 Granulometric parameters of Jamne stream. Cross section

No point

I

1 2 3 1 2 3 4 1 2 3

dm

U

e

2.05 2.1 1.58 4.38 3.07 2.84 1.98 2.28 2.16 2.32

8.93 5.59 3.82 10.67 7.6 5.75 4.94 7.31 5.11 4.33

[m]

II

III

0.051 0.089 0.055 0.063 0.091 0.121 0.08 0.083 0.132 0.131

Cd

S0

1.58 0.97 1.31 0.59 0.72 1.58 0.86 0.62 1.31 0.61

1.5 1.45 1.41 1.79 1.47 1.6 1.26 1.3 1.49 1.25

[–]

Explanations: dm – mean grain diameter [m], U – Hazen’s sorting coefficient [–], e – Knoroz’s grain-size diversity indicator [–], Cd – Kollis’ uniformity indicator [–], S0 – the Trask’s sorting coefficient [–].

235

whereas the height of the banks was about 2 m. In that reach, the watercourse was oriented straight toward the Ochotnica River mouth. On the right side of the bank there was a gravel bar with finer material on it. In the cross-section III, the maximum water depth was Hmax = 0.20 m and velocities were within the range of V = 0.111–0.368 m s1, so a more dynamic situation was observed here than in the cross-section II. Shear stress values in cross-section III were within the range of t = 0.129–0.167 N m2, and the Reynolds numbers from Re = 27,400 to 56,265. However, at point 1, the Re values were lower: Re = 2128–2676. During the measurement periods, turbulent movement was observed. The Froude number values were from Fr = 0.163 to 0.283, and every point was similar. All the above mentioned parameters showed subcritical movement at cross-section III (Table 2 and Figs. 2 and 3). The mean grain diameter of sediment here was dm = 131–132 mm; only at point 1 was it lower: dm = 83 mm. The lower values of mean grain diameter at that point might be due to smaller shear stresses (Table 3 and Fig. 2). According to the Hazen and Trask sorting coefficients, the bed material was well sorted (U < 5 and S0 < 1.50). Only at two points, no. 1 and 3 in the Jamne II cross-section, was the Trask sorting coefficient equal, S0 < 1.50, indicating that the bed material was moderately sorted. On the left side and in the central part of the river channel, the size of the bed materials was very heterogenous (e > 5). At the other measurement points, which were located on the right side of the watercourse, the bed material was homogenous (e < 5) (Table 3). Along the Jamne stream, an increase in the dimensions of the bed material fraction was observed. At the Jamne I cross-section, dm = 65 mm was observed; in the middle part at Jamne II, dm = 89 mm occurred and this was larger than previous number observed at Jamne I. Finally at Jamne III, dm = 116 mm, which was the largest value. This was an interesting observation since the particles usually got smaller going downstream along the river course. The enlarging of the dm along the longitudinal profile of the river might show that the fine sediment fractions were removed by smaller discharges and, with no huge flows present in the river channel, new sediment is not transported. At the same time, river bank erosion was stopped by some river engineering works so finally we had some incision along river course with a coarsening of the sediments along the Jamne stream longitudinal profile (Figs. 2 and 5). 4.2. Jaszcze stream In the Jaszcze stream, cross-section I was localized approximately 6.8 km upstream from the Ochotnica River estuary, in a deeply cut and forested part of the valley. The watercourse was cut into solid rock and its current was straight. The width of the river channel in the measurement cross-section was 8.15 m, whereas the height of the right bank was about 1 m and the left one about 1.8 m above river bed in the thalweg. There were rock outcrops exposed above the cross-section. On both sides of the

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Table 4 Hydrodynamic parameters of Jaszcze stream. Cross section

No point

vav

Hmax

vmax

[m] 1 2 3 4 1 2 3 4 1 2 3 4

I

II

III

[m s

0.1 0.09 0.04 0.1 0.07 0.1 0.16 0.18 0.15 0.13 0.13 0.08

0.072 0.083 0.113 0.583 0.148 0.1 0.244 0.394 0.345 0.244 0.55 0.192

v*

1

t

Reav 2

]

[N m

0.111 0.103 0.129 0.66 0.31 0.145 0.384 0.52 0.43 0.36 0.7 0.232

0.007 0.008 0.006 0.036 0.027 0.007 0.012 0.031 0.013 0.01 0.034 0.007

0.045 0.062 0.031 1.265 0.725 0.048 0.135 0.941 0.182 0.107 1.177 0.052

]

Remax

Redm

Frav

380 700 713 2145 1482 859 1157 2283 835 725 2298 478

0.072 0.088 0.18 0.589 0.178 0.101 0.194 0.297 0.284 0.216 0.487 0.217

[–] 5479 5711 3455 44,594 7908 7619 29,804 54,216 39,574 24,265 54,659 11,749

8486 7087 3945 50,455 16,589 11,085 46,969 71,554 49,308 35,777 69,567 14,189

Frmax [–] 0.112 0.11 0.206 0.666 0.374 0.146 0.307 0.391 0.354 0.319 0.62 0.262

Notations like in Table 1.

watercourse, gravel bars were present. On the right bank, a tiny erosive undercut appeared. In the Jaszcze stream (when during the measurements the observed discharge was Q = 1.2 m3/s at the Ochotnica River outlet), the cross-section I water height was within the range of H = 0.04–0.1 m. The velocities of flow at point 4 were V = 0.583–0.66 m s1. At the other measurement points, velocities were significantly lower, from V = 0.072 m s1 to 0.129 m s1. The high velocities at point 4 influenced the other hydrodynamic parameters values here. Shear stress was t = 1.265 N m2 which was the highest value of that parameter at all measurement points across the three cross-sections on the Jaszcze stream. The Reynolds number values as well as the Froude numbers were Re = 44,594–50,455 and Fr = 0.589–0.666, respectively. These were also much higher than in the remaining cross-sections. At points 1, 2 and 3, the values of the discussed parameters were much lower: t = 0.031– 0.062 N m2, Re = 3455–8486 and Fr = 0.088–0.206. In this cross-section, turbulent and subcritical movements were observed (Table 4 and Figs. 3 and 4). At Jaszcze I, the mean grain diameters were dm = 74– 168 mm. At point 4, apart from the high velocity of flowing water V = 0.583 m s1, the mean grain diameter value of the sediment deposited here was only dm = 79 mm (Table 5). At cross-section 1, there were many rock

Table 5 Granulometric parameters of Jaszcze stream. Cross section

No point

dm

U

e

[m] I

II

III

1 2 3 4 1 2 3 4 1 2 3 4

Notations like in Table 2.

0.074 0.116 0.168 0.079 0.072 0.162 0.13 0.097 0.081 0.092 0.088 0.087

Cd

S0

1.17 1 0.84 1.14 1.12 0.83 0.79 1.26 1.17 1.04 0.93 0.75

1.34 1.78 1.51 1.32 1.51 1.32 1.65 1.51 1.45 1.3 1.32 1.6

[–] 1.65 2.5 2.87 1.95 1.74 1.85 2.66 2.44 2.05 1.6 2.56 2.24

3.71 5.56 6.88 3.61 4.96 3.13 8.88 6.41 3.43 4.05 9.69 4.11

outcrops as well as over-sized grains between which tiny materials were packed. They created interstitial spaces which were suitable for invertebrates. The river bed here was much coarser then in other places, and we noticed increases in the dynamics and turbulence of the stream, where mean water velocity was up to V = 0.238– 0.24 m s1. Also the instantaneous velocity values measured just above the river bed were an important parameter for transported material estimation, not just mean velocity and shear stress (Fig. 4). The second cross-section (Jaszcze II) is located approximately 4.9 km from the Ochotnica River estuary, in the middle part of the Jaszcze valley. The width of the river channel at the measurement cross-section was 5.75 m and it was cut into solid rock. It was not forested but was meandrous. The height of the left bank was about 2.30 m. This bank was intensively undercut, revealing rock outcrops that supplied the stream bed with rocky material. The right bank height was about 0.30 m. There was a gravel bar next to the Jaszcze II cross-section. At cross-section II, the velocity values on the left side of the river bed (points 1 and 2) were lower (V = 0.1– 0.31 m s1) than the values on the right side of the watercourse (points 3 and 4; V = 0.244–0.52 m s1 where water depths were between H = 0.16 m and H = 0.18 m) where the main current was situated. Shear stress values were highest at points 1 and 4 and were t = 0.725 N m2 and t = 0.941 N m2, respectively. The Reynolds numbers and Froude numbers were highest at points 3 and 4 and their values were Re = 29,804–71,554 and Fr = 0.194–0.391, respectively. Turbulent and subcritical movements were noticed. On the other side of the watercourse, at points 1 and 2, the Reynolds number values were lower, Re = 7619– 16,589, but turbulent movement was still present. However, the Froude numbers were slightly lower, between Fr = 0.101 and 0.374. As in cross-section I, rock outcrops as well as over-sized grains were present, which resulted in the highest mean grain diameter values, dm = 130–162 mm, occurring in the middle part of the cross-section. In the side parts of the cross-section the size of the sediment was dm = 72–97 mm (Tables 4 and 5 and Figs. 3 and 4). The third cross-section (III) was located in the lower part of the Jaszcze valley, approximately 260 m from the Ochotnica River estuary, where the stream bed was

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237

Fig. 4. Velocities, water depth at the measurement points and the mean diameter of bed materials at Jaszcze stream.

engineered and reinforced on both sides with concrete banks about 250 m long, running up to the Ochotnica River mouth. The width of the stream bed at the measurement place was 6.15 m, whereas the heights of the right and left banks were 1.3 m and 1.7 m, respectively. There was a gravel bar next to the right bank. Above the studied crosssection, the stream bed meandered, and was deeply incised and cut into the solid rock with numerous rock outcrops which were being destroyed by the erosive processes that occur there (Niemirowski, 1974). At cross-section Jaszcze III, mean velocity values were diverse. They ranged from values of V = 0.192 m s1 at point 4 to V = 0.55 m s1 at point 3. Despite diverse flowing

water velocities, the sizes of the sediment in the whole cross-section were similar, with dm = 81–92 mm. The highest shear stress was present at point 3, t = 1.177 N m2. At the remaining points, stresses were lower, t = 0.052–0.182 N m2. The Reynolds numbers were Re = 11,749–69,567, which meant that turbulent movement occurred. The Froude number values were the highest at point 3, ranging between Fr = 0.487–0.62, whereas they were lower at the remaining points Fr = 0.216–0.354. Subcritical movement of water occurred there. The gravel deposited was moderately sorted. Mean grain diameter along the Jaszcze stream changed significantly. In cross-sections I and II, where natural segments

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Mean diameter - dm [m]

238

0.180

macrobenthos (Kłonowska-Olejnik and Radecki-Pawlik, 2000; Zase˛pa et al., 2006).

0.160

4.3. Invertebrate communities and the BMWP-PL index in the Jamne and Jaszcze streams

0.140

In the Jamne and Jaszcze river channels, during July and November, surveys were performed at 3 study sites (Tables 6 and 7). Benthic measurements, performed on the Jamne and Jaszcze streams during July and November 2013, led to the approximate classification of the taxonomic status at specific cross-sections of the analyzed streams and showed differences in cross-sections species composition, depending on the state of the water (in July the water level was slightly higher). This allowed the assessment of ecohydrological status of the small mountain rivers using the invertebrate fauna which also in highlighted knowledge of other hydrodynamics parameters. In terms of species richness (the absolute number of taxa identified to the lowest level of a systematic), the Jaszcze stream (20 taxa – in July and 19 November) outweighed the Jamne stream (16 taxa were found in July and 14 in November). It is difficult to treat this result as diagnostic but a clear trend was confirmed during the two sampling periods. This was connected with the hydrodynamics of the particular cross-sections as well as changes with the granulometry of the two streams. Sediment grain size is of prime importance for invertebrate fauna (Tables 2–5) since the Jamne I and Jaszcze I sections were the cross-sections in natural condition (unmanaged) and the Jamne II and III and Jaszcze II and III cross-sections were managed or partly managed.

0.120 0.100 0.080 0.060 0.040 0.020 0.000 JAMNE I

JAMNE II

JAMNE III

JASZCZE I

JASZCZE II

JASZCZE III

Fig. 5. The distribution of mean diameter at the research cross sections.

appeared, their values were close to each other, dm = 109 and dm = 115 mm (Tables 4 and 5 and Figs. 3–5). Generally, on the Jaszcze stream bed, the bed materials were less sorted than on the Jamne. The Trask sorting coefficients were in the range of S0 = 1.30–1.78. However, the Hazen sorting coefficients were similar to those found on the Jamne (U < 5). On the right side of the river channel, the sizes of the bed materials were very heterogenous (e > 5), while, on the left side, the bed materials were homogenous (e < 5) (Table 5). At cross-section Jaszcze III, the size of the gravel was dm = 87 mm, which might be due river engineering works, although a quite coarse gravel bar was present here. In regulated channels, especially those engineered using materials such as concrete, the flowing water rises much higher than in natural river channels. The flow is influenced by the small value of roughness created by the revetment walls, the lack of stream gravel bars on the river bed as well as flow concentration. The stream water which flows with such great velocity washes away the sediment which was earlier eroded and, after traveling some distance, was later deposited. Material in the crosssection was most often homogenous without bed forms. Such conditions hamper water organisms and discourage

Table 6 Benthic invertebrate taxa recorded during July 2013 surveys performed in cross-sections of Jamne (J1, J2, J3) and Jaszcze (S1, S2, S3) streams and the score assigned to each taxon in the BMWP-PL index. The values in the tables are: the number of the specimen found in the cross-section, in bracket – the BMWP-PL value. Taxa/stream cross-section Dendrocoelum carpathicum Nematoda Erpobdella octooculata Gammarus sp. Capnidae Chloroperlidae Leuctra sp. Perla sp. Perlodes sp. Teaniopterygidae Baetis sp. Caenis sp. Ephemerella sp. Ephemera sp. Heptagenidae Leptophlebia sp. Hydropsyche sp. Goera sp. Chironomidae Simulium sp. Tabanus sp. Index BMWP-PL Ecological class numer

J1

J2 1(X) 2(X) 1(3)

2(8) 1(8) 2(7) 1(7) 2(9) 2(6) 1(7) 2(7)

2(8) 1(8) 2(7) 2(7) 3(9)

J3

S1

2(X)

3(8) 1(7) 1(7) 2(7) 2(9)

2(7) 6(7) 2(7) 1(6)

2(7) 4(7)

3(5)

4(5)

4(6) 1(8) 2(8)

2(X) 2(3) 2(6) 2(8) 1(8)

1(7)

1(7) 2(7)

3(6) 2(7) 1(7) 2(7)

2(6) 1(5) 6(9)

2(3) 2(X) 59 III

1(X) 74 II

S2

2(X)

2(X) 66 III

2(X) 70 II

2(6) 4(7) 2(7) 2(7) 1(6)

S3 2(X) 1(X) 3(6) 1(8) 1(7) 2(7) 1(9) 3(6) 2(7) 2(7) 3(6)

2(5)

3(5)

2(3) 3(6) 6(X) 86 II

1(3) 1(6) 2(X) 77 II

A. Radecki-Pawlik et al. / Ecohydrology & Hydrobiology 14 (2014) 229–242 Table 7 Benthic invertebrate taxa recorded during November 2013 surveys performed in cross-sections of Jamne (J1, J2, J3) and Jaszcze (S1, S2, S3) streams and the score assigned to each taxon in the BMWP-PL index. The values in the tables are: the number of the specimen found in the crosssection, in bracket – the BMWP-PL value. Taxa/stream cross section Nematoda Gammarus sp. Capnidae Chloroperlidae Leuctra sp. Perla sp. Perlodes sp. Teaniopterygidae Baetis sp. Caenis sp. Ephemerella sp. Ephemera sp. Heptagenidae Leptophlebia sp. Hydropsyche sp. Goera sp. Chironomidae Simulium sp. Tabanus sp. Theodoxus fluviatilis Index BMWP-PL Ecological class numer

J1

J2

J3

S1

2(X)

S2

S3

2(X) 4(6)

1(8) 2(8)

2(8)

2(8) 2(8)

3(8)

2(7) 1(7) 2(9) 2(6) 1(7) 2(7)

2(7) 1(9) 2(7) 3(7) 2(7)

1(7) 2(7) 2(9) 3(7) 2(7)

1(7) 3(6) 2(7)

1(7) 2(7) 2(6) 3(7) 2(7) 2(7)

2(6) 1(5)

2(5)

2(X)

1(X)

57 III

57 III

2(5)

48 III

1(7) 2(5) 2(9)

2(X) 1(6) 61 III

2(7) 1(9) 3(6) 3(7) 1(7) 2(6)

2(5)

2(5)

1(3) 2(6) 2(X)

1(X)

63 III

55 III

The specificity of the invertebrate fauna, the changes in taxonomic composition and their proportions were mainly related to transformations of individual species. The small distances separating the different streams (and sampling cross-sections), and the absence of certain taxa in the Jamne stream (scuds, Leptophlebia sp., Simulium sp., Psychedelic sp.) suggests that ‘‘temporary absence’’ of species was not the result of reproduction. In such a case, the granulomenric and hydrodynamics conditions in a particular cross-section would be the most important factor governing the benthic species which were present or absent. At the same time, as was indicated before, in the regulated parts of the both streams, hydrodynamic parameters (especially mean velocity and shear stress) were found to be higher than in the unregulated parts. Higher forces that have an effect upon the watercourse channel bed as well as high water flow velocities combine to activate and transport sediments with greater diameter, causing degradation of the stream and leaving only homogenous material in the bed. That is undoubtedly the main factor determining taxonomic diversity in the individual cross-sections. Small differences in microhabitats can result in the scarcity of ecological niches for more species. For comparison with other rivers in the Polish Carpathians that have been recently analyzed, 35 taxa were found in the Czarny Dunajec River, 31 taxa in the Raba River, and 43 taxa in the Biała Tarnowska River (Wyz˙ga et al., 2013). But one has to consider that the research on these rivers has been performed for years, and the measurements of cross-sections (number of reaches and microhabitats) was much greater. The BMWP-PL index, used to assess the ecological status of the Jamne and Jaszcze streams, was relatively

239

balanced and fluctuated between class II and class III. In light of the other studied rivers in the Polish Carpathians (Wyz˙ga et al., 2013), the Biała Tarnowska and the Raba individual cross-sections, the BMWP-PL values ranged from I to IV. Significant is the fact that one channel crosssection (all of the Jaszcze and the Jamne streams are a single thread cross-section), with few exceptions, usually are characterized by values BMWP-PL equal to or higher than class III (i.e. classes III, IV or V). In this respect, the biological value of the Jamne and Jaszcze streams must be considered as high. 4.4. Linking ecohydrological parameters with the Jamne and Jaszcze stream cross-sections First of all, it has to be said that the cross-sections associated with the hydromorphological and hydrobiological surveys were the same for both streams, so this analysis was possible. Looking into the data taken from hydrodynamic, granulometric and hydrobiological observations of the Jamne and Jaszcze streams. One has to bear in mind the small number of observations as well the scarcity of data on some parameters possibly needed to deepen interpretations. This places some limitations on the interpretation of the benthic invertebrate index values. On the other hand, the river management staff and engineers would be unlikely to want to spend more time collecting these additional data to assess, for example, the ecohydrological status of any stream, given the need to work on hundreds of streams in Poland not yet having an accepted hydromorphological assessment. Nevertheless, the data that were collected showed that both streams had large numbers of invertebrates which was quite important as an indicator of their biological status. In the Jaszcze stream during the two seasons of sampling we noticed that the stream achieved class II water ecological status according to RMS (2004) on three occasions during July. At the same time, we noticed the same situation only once on the Jamne stream. November measurements gave slightly worse results, showing that taxa were less important as biological indexes although the ecological class number was still not so low. However, as it was said before, generally fewer taxa were found in November which might indicate, for the future, that invertebrate collections should be concentrated on summer months rather than the fall. It might be said that taxa found in July would be likely to have a lower tolerance for pollutants when sitting in warmer water than when living in colder water in the fall when pollutants are not so strongly affecting invertebrates. In Jamne cross-section II (Jamne II) we noticed the smallest values of Fr numbers (Fr = 0.063–0.224) which would indicate a lack of turbulence so this section would potentially be richer in taxa than others. At the same time, the shear stresses were not moving sediment since the threshold values at all 4 measuring points were below the sediment movement threshold for that cross-section (t = 0.007–0.121 N m2). Also, all sediment parameters, especially the Trask sorting coefficient as well as the Hazens sorting factors had the best values when comparing them with the other values in all other cross-sections of the Jamne stream. The worst

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situation was at Jamne III where the BMWP-PL was smaller, placing this station into the III ecological class. Here one can notice that all the shear stress values (from t = 0.129 N m2 to t = 0.138 N m2) were sufficient to move sediment of the mean grain diameter. Also the Re number values were quite high, up to 56,265. But the greatest shear stress t values were at Jamne I in the central part of the cross-section (t = 1.51 N m2), where the sediment threshold movement for a mean grain diameter dm = 0.089 m was the highest and the sediment was moving freely. Thus erosion p takes place here which has a direct influence on taxa. This is indicated by the smaller number for the BMWP-PL here (57 in July and 59 in November) and the III ecological class rating. Having knowledge of the Jamne stream river engineering works undertaken to protect the local road and of the middle part of Jaszcze catchment where some improvements of revetment walls had taken place, it would seem that those works had no very important influence on the ecohydrological status of the river channel there. But it has to be said that only one of the river banks was protected with gabions (no concrete was used for bank reinforcement) and no engineering works had been done in the river bed. It is rather the incised upstream part of the Jaszcze catchment with observed erosion where the ecohydrological parameters were the worst and this section needs to be looked at more carefully for reasons of stream channel incision here and possibly one could let the river become broader in that particular section. The Jaszcze stream in all its cross-sections was rated as ecological class number II in July which indicated that the stream taxa had a low tolerance for pollutants and that they were a good hydrobiological indicator. The Jaszcze I crosssection from the left bank to 2/3 of the channel width had a sediment shear stress threshold insufficient to move sediments downstream (t = 0.031–0.062 N m2), whereas at the right bank the shear stress t = 1.265 N m2 was strong enough to move sediments with a mean grain diameter up to 0.079 m. Erosion has taken place here and it might have had an influence on the taxa, since the BMWPPL index here was the worst in July. Notwithstanding, the taxa were adequate to bringing this cross-section into the II ecological class. Also the Fr number for the right bank was quite high (Fr = 0.666) which might have had an influence on sediment movement and its associated parameters. The Trask sorting coefficient was higher here (1.78) than elsewhere which possibly had a negative influence on the taxa at the right bank of this cross-section. At Jaszcze II, the shear stresses were low at the left bank (from t = 0.048 N m2 up to t = 0.725 N m2) and were below the movement threshold (mean grain diameter here is from 0.072 m to 0.162 m), whereas, on the right bank, shear stresses were greater (t = 0.135–0.941 N m2) with quite high Re numbers were high (Re = 46,969–71,554) and sediment movement was noticed here. But one has to notice the high Kollis uniformity indicator (1.26) which is a very good value for invertebrates living there. Thus in general this cross-section was the best as far as ecohydrological parameters were concerned. This was due to the variability of the different hydrodynamic as well as granulometric parameters. On the other hand, Jaszcze I

and Jaszcze II were not engineered in any way. The worst situation was at Jaszcze III, where the whole cross-section of the stream was river engineered including the river bed. The uniformity indicator (0.75) and Hazen sorting coefficient values were the lowest here, whereas the grain size diversity factor was maximal (9.69). Shear stresses here were from t = 0.052 N m2 to t = 1.77 N m2 causing sediment to move in the middle part of the cross-section. Also all Re and Fe numbers were the highest (Re up to 69,567 and Fr up to 0.62). But the conditions here for invertebrates were not so bad. Nevertheless, the II ecological class was found here in July. What was noticed in that location was the many types of sediment that were deposited on both banks of regulated cross-section and that only the middle part has bad ecohydrological conditions. It has to be said that previous engineering management works in Poland required people to clean up sediment from such regulated river beds. Recent river management practices do not allow removal of sediments and many small gravel bars have started to develop on engineered river beds which might have had positive influence on habitat conditions improving the ecohydrological processes here. Finally it must be said that BMWP-PL index was designed for the assessment of the ecological quality of rivers and might not appropriately capture the hydrodynamics of streams and other features which are connected to its morphology or the kinds of materials from which the river channel was built. So limitations on the benthic invertebrate index are obvious. However, as we discussed here and as noted in Wyz˙ga et al. (2013), one has to agree that the extension of the index from BMWP to BMWP-PL has given the index a larger scale, with a range of numbers and values for the index that are more sensible for evaluating the presence of invertebrates. Thus, these analyses might be best done not only along the stream in longitude profile but also along cross-sections which very much enrich knowledge of the ecological status of the river. Thus, having additional hydrodynamic and granulometric data one could develop a nice overview of the river. However in our opinion the most important thing would be that anybody dealing with the hydromorphological assessment of a particular river must know it pretty well before providing an opinion. Additionally we think that, for such ecohydrological conditions which include the presence of macro-benthos, as in the case of one thread channels similar to those of both the Jamne and Jaszcze, the microhabitats and the number of species will have a greater influence as we start suffer from a scarcity of water: low stages in both streams are present during nearly all the year (Radecki-Pawlik, 2011). These must be connected also with water temperature, conductivity, oxygen and possibly woody debris (Wyz˙ga, 2007) as well as bankfull discharge assessment especially using biotic methods which use living organisms as indicators (Radecki-Pawlik and Skalski, 2008a,b; Skalski et al., 2012). Finally sediment transport analysis and turbulence data might be very useful to an understanding, in very detailed way, of the state of hydrodynamic equilibrium in the analyzed stream channels which have a huge influence on the living conditions of the benthos.

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5. Conclusions

Financial disclosure

From the analyses conducted of the selected ecohydrological (hydrobiological and hydrodynamic) parameters measured in this study of the Jaszcze and Jamne streams, some general conclusions can be drawn, which might be considered also in case of other small mountainous gravel bed streams:

This work was financially supported by Department of Hydraulic Engineering and Geotechnic, University of Agriculture in Krakow and Department of Geoenvironmental Research, Institute of Geography and Spatial Organization, Polish Academy of Sciences.

1. In the regulated parts of the investigated mountainous streams, hydrodynamic parameters (especially mean velocity and shear stress) were found to be higher than in the unregulated parts. High forces that have an effect upon the watercourse channel bed as well as high flowing water velocities combine to mobilize and transport sediments with a greater diameter, causing degradation of the stream and leaving only homogenous material in the bed. It has consequences for macrobenthos assemblages, their species richness and the presence of particular taxa. 2. In natural, unmanaged mountain gravel stream beds, values of instantaneous flow velocity are characterized by greater variability (which is associated with turbulent water) than those from the managed parts. It has consequences both on sediment movement and taxa richness. 3. Concrete hydraulic structures situated in the watercourse influence river bed hydrodynamics, most often demonstrated by the removal of coarse sediments and an increase in water velocity. This leads to a loss of some micro-benthic taxa due to lack of microhabitats and, as a consequence, a scarcity of ecological niches for more species. The presence of such hydraulic structures also leads to a loss of interstitial spaces and increased water velocities. 4. Mean grain diameter of sediment deposited in the Jaszcze stream bed increased along its banks which testified to the rocky material supplementing the bed resulting from side bank erosion. This phenomenon was not observed in the Jamne stream where river bed material size was similar along the whole watercourse length. This might be associated here, as well as in another mountain small gravel stream environments, with the very sensitive reaction to changes in the river channels by management practices. It leads to the conclusion that, in small mountain creeks, one must pay special attention when applying any kind of river training. If such training is needed it must be developed in consultation with hydrobiologists and fluvial geomorphologists so as not to spoil the natural habitats of invertebrates. 5. Ecohydrological insights into the small creaks with gravel beds are essential when analyzing management practices in river channels. They must consider both hydrodynamics and hydrobiology, and, as background, consider both the geology and sediments of the particular cross-section of the stream.

Conflict of interest None declared.

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