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Evaluation of drought conditions in the northern regions of South Africa
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BOOK REVIEWS
Many areas of the USSR lose a great amount of water through nonproductive evaporation. According to data of the Institute of Geography of the USSR Academy of Sciences this share of non-productive evaporation of the USSR territory comprises 58 per cent. The main volume of the nonproductive evaporation relates to useless soils, meadows and pastures covered with vegetation uneatable by cattle. A great part of the evaporation from certain soils is due to that from cane undergrowths and other phreatophytes growing in valleys and deltas of rivers in the southern and south-eastern part of the country. These plants are not suitable for cattle forage. The total area of cane undergrowths in these areas is about 4 million hectares. There are different opinions about the rate of evaporation from cane undergrowths. Some observers consider that evaporation from these undergrowths is less than that of the open water surfaces. Investigation of the rates along the Kara-Kum Canal crossing the sand desert for a great distance showed that under such conditions the evaporation from the cane undergrowths could be five times higher than that from the water surface and comprise 9000 rom per year. A study of the heat balance showed that the heat losses for evaporation greatly exceed the residual radiation and that the heat source for evaporation will be mostly the flow of the heated air masses from the surrounding desert. Assuming that in arid zones of the USSR evaporation from cane undergrowths and other phreatophyte plants in flood-lands and river deltas requires all the heat from the sun radiation, then the mean value of evaporation will be 2,200 rom per year and the total amount of non-productive evaporation will be 180 kID? i.e. three times higher than the amount withdrawn for irrigation. (From Author's Abstract). D. C. LEWIS and R. H. BURGY: Hydraulic characteristics of fractured and jointed rocks. Ground Water, 2, no. 3 (July 1964) pp. 4-9, 10 figs., 2 tables. D. F. ROBERTS: The empirical determination offlood peak probabilities. Tech. Ref. No. 33. Hydrological Research Division, Dept. of Water Affairs, Pretoria, Rep. S. Africa (1965). Tables and graphs. P. H. HERBST: Report on tests on evaporation suppression carried out at Pienaars River dam. Tech. Rep. No. 34. Hydrological Division, Dept. of Water Affairs, Pretoria, Rep. S. Africa (1965) p. 29. Illus., tables, graphs.
Evaluation ofdrought conditions in the northern regions of South Africa. Tech. Rep. No. 35. Basic Research Section, Hydrological Research Division, Dept. of Water Affairs, Pretoria, Rep. S. Africa (1965) p. 9. Tables and maps.
BOOK REVIEWS
Many areas of the USSR lose a great amount of water through nonproductive evaporation. According to data of the Institute of Geography of the USSR Academy of Sciences this share of non-productive evaporation of the USSR territory comprises 58 per cent. The main volume of the nonproductive evaporation relates to useless soils, meadows and pastures covered with vegetation uneatable by cattle. A great part of the evaporation from certain soils is due to that from cane undergrowths and other phreatophytes growing in valleys and deltas of rivers in the southern and south-eastern part of the country. These plants are not suitable for cattle forage. The total area of cane undergrowths in these areas is about 4 million hectares. There are different opinions about the rate of evaporation from cane undergrowths. Some observers consider that evaporation from these undergrowths is less than that of the open water surfaces. Investigation of the rates along the Kara-Kum Canal crossing the sand desert for a great distance showed that under such conditions the evaporation from the cane undergrowths could be five times higher than that from the water surface and comprise 9000 rom per year. A study of the heat balance showed that the heat losses for evaporation greatly exceed the residual radiation and that the heat source for evaporation will be mostly the flow of the heated air masses from the surrounding desert. Assuming that in arid zones of the USSR evaporation from cane undergrowths and other phreatophyte plants in flood-lands and river deltas requires all the heat from the sun radiation, then the mean value of evaporation will be 2,200 rom per year and the total amount of non-productive evaporation will be 180 kID? i.e. three times higher than the amount withdrawn for irrigation. (From Author's Abstract). D. C. LEWIS and R. H. BURGY: Hydraulic characteristics of fractured and jointed rocks. Ground Water, 2, no. 3 (July 1964) pp. 4-9, 10 figs., 2 tables. D. F. ROBERTS: The empirical determination offlood peak probabilities. Tech. Ref. No. 33. Hydrological Research Division, Dept. of Water Affairs, Pretoria, Rep. S. Africa (1965). Tables and graphs. P. H. HERBST: Report on tests on evaporation suppression carried out at Pienaars River dam. Tech. Rep. No. 34. Hydrological Division, Dept. of Water Affairs, Pretoria, Rep. S. Africa (1965) p. 29. Illus., tables, graphs.
Evaluation ofdrought conditions in the northern regions of South Africa. Tech. Rep. No. 35. Basic Research Section, Hydrological Research Division, Dept. of Water Affairs, Pretoria, Rep. S. Africa (1965) p. 9. Tables and maps.