Water loss in the discharge system The amount of water lost through
seepage in the new run-off and drainage system increased from 2 billion
m3
 to 16 billion m3
 annually between 1964 and 1972 (CAPMAS 1987: 144ff ).
There are two main reasons for this, the first of them being the fact that,
unlike formerly, when there was a water shortage, people now do not use
water economically but irrigate excessively, because they have free access to
it. The second reason is that frequently water is let out through the dam
merely because it is required for the production of hydroelectric power, or
because it is necessary to raise the water table for purposes of navigation.
This is particularly so in winter, when less water is needed on the fields. The
amount of water lost in this way since the construction of the High Dam is
calculated at 2.4 billion m3
 annually (see Table 6.1).