chapter - Atmospheric and Oceanic Science

The main services and problems of water resource
8.3. Main services of water resources
8.3.1. Water supply and urban drainage
Water availability below 1000 m 3 / per capita /year, characterizes a water stress
scenario. At a regional level, all of the countries of the La Plata basin are over this
value. Even though South America has the 28% of the global water resources, there
is a great spatial and temporal (interannual and within the year) variability, and
therefore, there are events of water stress.
Consumption uses of the countries of the La Plata basin are presented in table
8.1 in percentages of the total. It can be seen that in all the countries, farming is the
sector with the highest consumption of water.
Table 8.1. Use of water per sector in %, 1999.
Country Residential Industrial Farming
Argentina 9 18 73
Bolivia 10 5 85
Brazil 22 19 59
Paraguay 15 7 78
Uruguay 6 3 91
[GWP 2000]
In some large cities, water utilities and their distribution systems are not
enough for the extraordinary demand during extreme droughts. In these circumstances,
water utilities have to operate beyond their technical margins because their
water intakes are compromised fore the reduced water flow level. Thus, palliative
measures such as massive perforation of new underground wells are taken, which
in turn cause a substantial reduction of phreatic levels.
Large supply problems take place at the headwaters of basins where large
urban concentrations exist, such as Sao Paolo, Curitiba and Campo Grande in
Brazil. For example at the beginning of October 2003, the water rationing in Great
Sao Paolo affected 440 thousand inhabitants. The Pedro Beicht dam, the only one
of the system, had to provide 1110 l/s and it was only producing 100 l/s . The capacity
of the reservoir was draining off at a rate of 0.4% per day, which led to the lowest
volume (7.6%) since its operation started in 1916. In the year 2000, it had
reached another low (14.6%) but not as serious level, (source Folha de São Paulo).
Likewise, water supply was unavailable in several parts of the city and surroundings
of Ciudad del Este affecting 50 thousand residents during April 2004. Because
of a severe drought, the República Lake that was the water pumping source reached
very low levels (source Diário ABC).
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