Water for people.pdf - WHO Thailand Digital Repository

4 7 0 / P I L O T C A S E S T U D I E S : A F O C U S O N R E A L - W O R L D E X A M P L E SLake Titicaca Basin, Bolivia and PeruWater ResourcesHydrologySurface waterAs described earlier, four main hydrographic basins form the TDPSsystem: Lake Titicaca is the main element. Its principal tributariesare located in Peruvian territory: Ramis and Huancané to the north,Coata and Illpa to the west, and Ilave and Zapatilla to the southwest.In Bolivia, the most important affluents are: Huayco, Suchezand Keka to the north and east, and Catari and Tiwuanacu to thesouth. The Ramis River is the most important as it represents26 percent of the tributary basin. Its flow is about 76 cubic metresper second (m 3 /s). Annual flow in ten stations of the system isshown in table 21.6.Overflow from Lake Titicaca, observed at the source of theDesaguadero River, amounts to 35 m 3 /s. This flow represents only19 percent of the inflow of the five main tributaries, demonstratingthe great volume lost through evaporation.Between 1914 and 1992, historic levels of variation took placeduring different cycles: a major cycle lasted twenty-seven to twentynineyears while an intermediate one lasted twelve to sixteen years.Lake-level oscillation in this period had an amplitude of 6.37 metrescompared to the average annual oscillation of about 1 metre.Map 21.3: Distribution of groundwater in the TDPS systemGroundwaterAs can be seen in map 21.3, the main aquifers are located in themiddle and lower basins of the Ramis and Coata Rivers, in the lowerbasin of Ilave River and in a strip that extends from Lake Titicaca toThe main aquifers are located in the middle and lower basins of the Ramis andCoata Rivers, in the lower basin of Ilave River and in a strip that extends from LakeTiticaca to Oruro, bordering the eastern ridge.Table 21.6: Annual flow in ten control stations of Lake Titicaca and Desaguadero RiverAverage Maximum MinimumRiver Station (m 3 /s) (m 3 /s) (m 3 /s)Ramis Ramis 75.6 130.4 24.4Huancané Huancané 20.0 38.8 6.9Suchez Escoma 10.6 18.9 4.0Coata Maravilla 41.5 75.5 2.4Ilave Ilave 38.5 96.6 5.0Desaguadero International 35.5 186.5 –3.5Desaguadero Calacoto 51.9 231.6 6.2Mauri Abaroa 4.9 9.8 2.3Caquena Abaroa 2.8 5.6 0.9Mauri Calacoto 18.6 31.8 5.7Desaguadero Ulloma 77.1 282.7 19.7Desaguadero Chuquiña 89.0 319.3 20.0The main tributary of the Lake Titicaca basin is the Desaguadero River, with an average annual discharge of 89 m 3 /s and a maximum of 319 m 3 /s.