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Radioisotope gauge for monitoring suspended sediment in rivers and streams
International Journal of Applied Radiation and Isotopes, 1967, Vol. 18, pp. 585-593. Pergamon Press Ltd. Printed in Northern Ireland
Radioisotope Gauge for Monitoring Suspended Sediment in Rivers and Streams C. A. ZIEGLER,
J.
PAPADOPOULOS
and
BACH
SELLERS
P a r a m e t r l c s Inc., W a l t h a m , Massachusetts
(Received 25 October 1966) T h e p r o b l e m of d e t e r m i n i n g the a m o u n t of w a t e r carried suspended sediment is of increasing i m p o r t a n c e in areas such as agriculture, n a v i g a t i o n a n d w a t e r conservation. C o n v e n t i o n a l p o i n t s a m p l i n g m e t h o d s h a v e p r o v e d i n a d e q u a t e to m e e t c u r r e n t hydrology p l a n n i n g needs because short t e r m c o n c e n t r a t i o n excursions c a n n o t be monitored. T o satisfy the need for a self-powered, continuous m o n i t o r i n g system, a gauge based o n the use of r a d i a t i o n from a radioisotope source, h a v i n g the capability of continuously m e a s u r i n g sediment c o n c e n t r a t i o n over a c o n c e n t r a t i o n r a n g e of 1000-50,000 p p m was designed, developed a n d tested. T h e system is c a p a b l e of o p e r a t i n g a n d recording d a t a u n a t t e n d e d for a period of 7-1/2 days on i n t e r n a l power, thus constituting a completely a u t o m a t i c m o n i t o r i n g system. T h e theory of operation, error analysis, calibration methods, o p e r a t i n g procedures, a n d test results, are presented. UNE JAUGE
RADIOISOTOPIQUE POUR LA MESURE DU S]~DIMENT SUSPENDU DANS LES FLEUVES ET RIVIl~RES L a question d e la mesure de la q u a n t i t d de sddiment s u s p e n d u d a n s l ' e a u poss~de u n e imp o r t a n c e croissante e n r a p p o r t a u x sujets tels q u e l'agrlculture, la n a v i g a t i o n et la conservation de l'eau. Les m~thodes conventionnelles de faire les 6chantillons d ' u n p o i n t ~t l ' a u t r e se sont montrdes insuffisantes A satisfaire les besoius courants de dressage des plans h y d r o loglques puisqu'il est impossible d e sulvre les excursions de c o n c e n t r a t i o n de petite pdriode. /kiln d e satisfaire le besoin p o u r u n syst~me de dosage c o n f i n u a y a n t sa p r o p r e source d'~nergie o n a dessln6, mis ~ p o i n t et ~prouvd u n e j a u g e qui emploie le r a y o n n e m e n t d ' u n e source radioisotopique, c a p a b l e de m e s u r e r c o n t i n f l m e n t la c o n c e n t r a t i o n d u sddiment p a r u n e g a m m e d e 1-000 A 50.000 p p m . Le systeme est c a p a b l e de f o n c t i o n n e r et d ' e n r e g i s t r e r les donn~es sans a t t e n t i o n d u r a n t u n e pdriode de 7½ j o u r s sur sa source d'~nergie int~rieure, ce q u i d o n n e u n syst6me d e mesure tout-~-fait a u t o m a t i q u e . O n prdsente la thdorie de f o n c t i o n n e m c n t , l'analyse des erreurs, les mdthodes d ' d t a l o n n a g e , les fa~ons d ' e m p l o i et les r~sultats des essais. PA~HOH3OTOIIHOE 7~CTPOI~CTBO ~ J I H H 3 M E P E H H H CYCIIEH3HPOBAHHbIX OCA~HOB B PEHAX H TEHEHHHX HpoS~eMa onpe~e~eHMA rco~HqecTBa cycneHa~poBaSH~X oca~RoB, nepeHoc~M~x BOROfl, HMeeT Bee yBe~HHBa~omeeca 8HaLIeHHe B TaHHx owpaC~HX Ha~ HaBHranIHa, ceabcRoe x0aHflCTB0, xpaHeHHe BOH~. OfHqn~m MeT0~BI BSflTHH 05paa~oB H8 pasH~X T0qe~ He M0ryT y~0BJIeTB0ptITB C0BpeMeHHbIe MeTORBI r n ~ p o n o r n q e c ~ o r o HJIaHIIp0BaHHH, TaR RaR ~paTHoBpeMeHH~e H3MeHeHHH HOHI~eHTpaI~HH He MOPyT 5BITB 3aMeqeHBL ~ n H yROBJIeTB0peHHH OTHX HyH~ 5 ~ n a pa3paSoTaHa CnCTeMa c C06CTBeHHBIMHCT0qHHHOM HHTaHHH HCHOJ~B3y~oI~a8 pa~naI~HIo 0T pa~HoaRTIIBHOPO HcToqHHHa H IIMeIomiaH CHOC06H0CTIa HsMepHTB ROHI~eHTpaI~IIH S n p e ~ e n e 0T 1.000 ~0 50.000 × 10-*. CHCTeMa 5BIJIa pa3BnTa n nposepeHa. OHa CII0C05Ha ReJ~aTB n 8aIIHCBIBaTb HsMepeHHH B TeqeHHH 7.5 RHefl, nCn0J~SyH BHyTpeHH~OIO 3HeprnIO, qT0 npeBpaL~aeT ee B aBTOMaTH'~ec~yIO naMepHIonlym cneTeMy. TeopnH ~eHCTBHH,anaJIn3 oInnSog, MeT0~BIHaoInfip0BHn,y n p a n e H n e npn6opoM H pesy~i~TaTBI HCIIBITaHIIi~IIIpe~CTaBJIeHbI B CTaTBe. 585
586
C. A. Ziegler, J. Papadopoulos and Bach Sellers RADIOISOTOPENMESSGER/~T ZUR KONTROLLE VON SCHWEBEGUT IN FLI~SSEN UND STROMEN Die Frage Bestimmung des Betrages des vom Wasser mitgeftihrten schwebegutes wird immer wiehtiger in Gebieten wie z.B. ira Ackerbau, in der Schiffahrt und in der Wasserwlrtschaft. Die fiblichen punktweisen Probeentnahmen waren unzureichend fiir die Zweeke der neuzeitlichen wasserwirtschafflichen Planung, well kurzzeitige Abschweifungen in der Anreicherung nicht kontroUiert werden k6nnen. Um den Bedarf ffir ein selbstst~nges ununterbrochen arbeitendes System zu decken wurde ein aufder Verwendung der Strahlung von einer Radioisotopenquelle beruhendes Messger~it, das ununterbrochen den Schwebegutgehalt tiber einen Anreicherungsbereich von 1000 bis 50,000 T.p. Mill. messen kann, konstruiert, entwickelt und geprtift. Das System kann ohne Wartung arbeiten und Daten registrieren tiber einen Zeitraum yon 7½ Tagen und hat eine eingebaute Kraftversorgung, sodass es ein vollkommen automatisches KontroUsystem darstellt. Es wird die Theorie der Wirkungsweise, die Fehleranalyse, Eichmethoden, Arbeitsweisen und Prtifergebnisse dargelegt.
INTRODUCTION THE DETERMINATION of the concentration of suspended sediment carried by natural and m a n - m a d e waterways is of increasing importance to agencies concerned with water conservation and control. Conventional point sampling methods have proven unsuitable in areas where difficulty of access, or flash floods and subsequent large, short term concentration excursions preclude an adequate sampling program. I n order to satisfy the need for a self-powered, continuous monitoring system a gauge based on the attenuation of radiation from a radioisotope source has been developed. Advantages of a radioisotope technique are first, because a b e a m of radiation is used as the sensing agent, the water and sediment are not perturbed, which permits greater accuracy than is obtainable using conventional mechanical sampling methods; and second, continuous sampling is possible with low power drain and high reliability. T h e latter is important inasm u c h as the gauge must operate continuously and unattended for a week at a time. I n order to arrive at the most appropriate system design three areas were investigated in detail: (a) because long term, unattended operation was desired it was necessary to develop an operational theory in the context of a stable self-referenced system; (b) since the radiation energy is of prime importance in determining attenuation gauge characteristics, a study to ascertain the most appropriate radioisotope source was carried out; and (c) a geochemical survey of the concentration levels and composition variation of both dissolved and
undissolved material at typical sites was made. This was necessary in order to predict gauge performance, because X- and g a m m a - r a y absorption depends on both the density and composition of the attenuating medium. Reports covering the above research are available from the Office of Technical Services, Departm e n t of Commerce, Washington, D.C. ~1'2'3~ T h e sediment gauge described in the following sections constitutes the end result of these preliminary studies. SYSTEM SPECIFICATIONS T h e development p r o g r a m for this system was sponsored by the Division of Isotopes Development, U.S.A.E.C. with the cooperation of the I n t e r Agency Sedimentation Project representing members of thirteen U.S. Agencies interested in sediment measurement. T h r o u g h the Technical Committee of the Sedimentation Project specifications were established representing the requirements of a gauge capable of widespread use within the continental U.S. Concentration range. 1000-50,000 p p m of sediment of density averaging 2"65 g/cm s. Accuracy. Better than : t : 2 0 ~ from 1000 to 50,000 p p m b y weight. Data retrieval. D a t a to be recorded permanently at 15 or 3 min intervals (real time) on tape capable of receiving data continuously over a 7½ day period without replacement. Environmental. Operational temperature-measuring head, 32-85°F; control unit, 20-120°F; survival temperature-measuring head and electronics -- 15-120°F.
Radioisotope Gauge for Monitoring Suspended Sediment in Rivers and Streams C. A. ZIEGLER,
J.
PAPADOPOULOS
and
BACH
SELLERS
P a r a m e t r l c s Inc., W a l t h a m , Massachusetts
(Received 25 October 1966) T h e p r o b l e m of d e t e r m i n i n g the a m o u n t of w a t e r carried suspended sediment is of increasing i m p o r t a n c e in areas such as agriculture, n a v i g a t i o n a n d w a t e r conservation. C o n v e n t i o n a l p o i n t s a m p l i n g m e t h o d s h a v e p r o v e d i n a d e q u a t e to m e e t c u r r e n t hydrology p l a n n i n g needs because short t e r m c o n c e n t r a t i o n excursions c a n n o t be monitored. T o satisfy the need for a self-powered, continuous m o n i t o r i n g system, a gauge based o n the use of r a d i a t i o n from a radioisotope source, h a v i n g the capability of continuously m e a s u r i n g sediment c o n c e n t r a t i o n over a c o n c e n t r a t i o n r a n g e of 1000-50,000 p p m was designed, developed a n d tested. T h e system is c a p a b l e of o p e r a t i n g a n d recording d a t a u n a t t e n d e d for a period of 7-1/2 days on i n t e r n a l power, thus constituting a completely a u t o m a t i c m o n i t o r i n g system. T h e theory of operation, error analysis, calibration methods, o p e r a t i n g procedures, a n d test results, are presented. UNE JAUGE
RADIOISOTOPIQUE POUR LA MESURE DU S]~DIMENT SUSPENDU DANS LES FLEUVES ET RIVIl~RES L a question d e la mesure de la q u a n t i t d de sddiment s u s p e n d u d a n s l ' e a u poss~de u n e imp o r t a n c e croissante e n r a p p o r t a u x sujets tels q u e l'agrlculture, la n a v i g a t i o n et la conservation de l'eau. Les m~thodes conventionnelles de faire les 6chantillons d ' u n p o i n t ~t l ' a u t r e se sont montrdes insuffisantes A satisfaire les besoius courants de dressage des plans h y d r o loglques puisqu'il est impossible d e sulvre les excursions de c o n c e n t r a t i o n de petite pdriode. /kiln d e satisfaire le besoin p o u r u n syst~me de dosage c o n f i n u a y a n t sa p r o p r e source d'~nergie o n a dessln6, mis ~ p o i n t et ~prouvd u n e j a u g e qui emploie le r a y o n n e m e n t d ' u n e source radioisotopique, c a p a b l e de m e s u r e r c o n t i n f l m e n t la c o n c e n t r a t i o n d u sddiment p a r u n e g a m m e d e 1-000 A 50.000 p p m . Le systeme est c a p a b l e de f o n c t i o n n e r et d ' e n r e g i s t r e r les donn~es sans a t t e n t i o n d u r a n t u n e pdriode de 7½ j o u r s sur sa source d'~nergie int~rieure, ce q u i d o n n e u n syst6me d e mesure tout-~-fait a u t o m a t i q u e . O n prdsente la thdorie de f o n c t i o n n e m c n t , l'analyse des erreurs, les mdthodes d ' d t a l o n n a g e , les fa~ons d ' e m p l o i et les r~sultats des essais. PA~HOH3OTOIIHOE 7~CTPOI~CTBO ~ J I H H 3 M E P E H H H CYCIIEH3HPOBAHHbIX OCA~HOB B PEHAX H TEHEHHHX HpoS~eMa onpe~e~eHMA rco~HqecTBa cycneHa~poBaSH~X oca~RoB, nepeHoc~M~x BOROfl, HMeeT Bee yBe~HHBa~omeeca 8HaLIeHHe B TaHHx owpaC~HX Ha~ HaBHranIHa, ceabcRoe x0aHflCTB0, xpaHeHHe BOH~. OfHqn~m MeT0~BI BSflTHH 05paa~oB H8 pasH~X T0qe~ He M0ryT y~0BJIeTB0ptITB C0BpeMeHHbIe MeTORBI r n ~ p o n o r n q e c ~ o r o HJIaHIIp0BaHHH, TaR RaR ~paTHoBpeMeHH~e H3MeHeHHH HOHI~eHTpaI~HH He MOPyT 5BITB 3aMeqeHBL ~ n H yROBJIeTB0peHHH OTHX HyH~ 5 ~ n a pa3paSoTaHa CnCTeMa c C06CTBeHHBIMHCT0qHHHOM HHTaHHH HCHOJ~B3y~oI~a8 pa~naI~HIo 0T pa~HoaRTIIBHOPO HcToqHHHa H IIMeIomiaH CHOC06H0CTIa HsMepHTB ROHI~eHTpaI~IIH S n p e ~ e n e 0T 1.000 ~0 50.000 × 10-*. CHCTeMa 5BIJIa pa3BnTa n nposepeHa. OHa CII0C05Ha ReJ~aTB n 8aIIHCBIBaTb HsMepeHHH B TeqeHHH 7.5 RHefl, nCn0J~SyH BHyTpeHH~OIO 3HeprnIO, qT0 npeBpaL~aeT ee B aBTOMaTH'~ec~yIO naMepHIonlym cneTeMy. TeopnH ~eHCTBHH,anaJIn3 oInnSog, MeT0~BIHaoInfip0BHn,y n p a n e H n e npn6opoM H pesy~i~TaTBI HCIIBITaHIIi~IIIpe~CTaBJIeHbI B CTaTBe. 585
586
C. A. Ziegler, J. Papadopoulos and Bach Sellers RADIOISOTOPENMESSGER/~T ZUR KONTROLLE VON SCHWEBEGUT IN FLI~SSEN UND STROMEN Die Frage Bestimmung des Betrages des vom Wasser mitgeftihrten schwebegutes wird immer wiehtiger in Gebieten wie z.B. ira Ackerbau, in der Schiffahrt und in der Wasserwlrtschaft. Die fiblichen punktweisen Probeentnahmen waren unzureichend fiir die Zweeke der neuzeitlichen wasserwirtschafflichen Planung, well kurzzeitige Abschweifungen in der Anreicherung nicht kontroUiert werden k6nnen. Um den Bedarf ffir ein selbstst~nges ununterbrochen arbeitendes System zu decken wurde ein aufder Verwendung der Strahlung von einer Radioisotopenquelle beruhendes Messger~it, das ununterbrochen den Schwebegutgehalt tiber einen Anreicherungsbereich von 1000 bis 50,000 T.p. Mill. messen kann, konstruiert, entwickelt und geprtift. Das System kann ohne Wartung arbeiten und Daten registrieren tiber einen Zeitraum yon 7½ Tagen und hat eine eingebaute Kraftversorgung, sodass es ein vollkommen automatisches KontroUsystem darstellt. Es wird die Theorie der Wirkungsweise, die Fehleranalyse, Eichmethoden, Arbeitsweisen und Prtifergebnisse dargelegt.
INTRODUCTION THE DETERMINATION of the concentration of suspended sediment carried by natural and m a n - m a d e waterways is of increasing importance to agencies concerned with water conservation and control. Conventional point sampling methods have proven unsuitable in areas where difficulty of access, or flash floods and subsequent large, short term concentration excursions preclude an adequate sampling program. I n order to satisfy the need for a self-powered, continuous monitoring system a gauge based on the attenuation of radiation from a radioisotope source has been developed. Advantages of a radioisotope technique are first, because a b e a m of radiation is used as the sensing agent, the water and sediment are not perturbed, which permits greater accuracy than is obtainable using conventional mechanical sampling methods; and second, continuous sampling is possible with low power drain and high reliability. T h e latter is important inasm u c h as the gauge must operate continuously and unattended for a week at a time. I n order to arrive at the most appropriate system design three areas were investigated in detail: (a) because long term, unattended operation was desired it was necessary to develop an operational theory in the context of a stable self-referenced system; (b) since the radiation energy is of prime importance in determining attenuation gauge characteristics, a study to ascertain the most appropriate radioisotope source was carried out; and (c) a geochemical survey of the concentration levels and composition variation of both dissolved and
undissolved material at typical sites was made. This was necessary in order to predict gauge performance, because X- and g a m m a - r a y absorption depends on both the density and composition of the attenuating medium. Reports covering the above research are available from the Office of Technical Services, Departm e n t of Commerce, Washington, D.C. ~1'2'3~ T h e sediment gauge described in the following sections constitutes the end result of these preliminary studies. SYSTEM SPECIFICATIONS T h e development p r o g r a m for this system was sponsored by the Division of Isotopes Development, U.S.A.E.C. with the cooperation of the I n t e r Agency Sedimentation Project representing members of thirteen U.S. Agencies interested in sediment measurement. T h r o u g h the Technical Committee of the Sedimentation Project specifications were established representing the requirements of a gauge capable of widespread use within the continental U.S. Concentration range. 1000-50,000 p p m of sediment of density averaging 2"65 g/cm s. Accuracy. Better than : t : 2 0 ~ from 1000 to 50,000 p p m b y weight. Data retrieval. D a t a to be recorded permanently at 15 or 3 min intervals (real time) on tape capable of receiving data continuously over a 7½ day period without replacement. Environmental. Operational temperature-measuring head, 32-85°F; control unit, 20-120°F; survival temperature-measuring head and electronics -- 15-120°F.