Water Users Association and Irrigation Management - Institute for ...

oads. It increases the base flow of rivers, thus indirectly causing erosion by deepening the
valley floor.
In regions where perennial irrigation makes possible two crops a year, correspondingly it
increases the period during which mosquitoes have habitats to breed. These mosquitoes
could be vectors of malaria, filariasis or Japanese encephalitis (Verghese 1990). The
resurgence of malaria in India appeared to coincide with the green revolution as the new
hybrid varieties demanded more intensive irrigation. Raichur district in Kamataka became
highly endemic for malaria after construction of the Tungabhadra dam (ERRC 1996). In the
Sirhind Feeder Canal Command Area, there is a "menacing increase in mosquitoes" (Dhesi
1996). States such as Punjab, Haryana, Andhra Pradesh and Uttar Pradesh have now
become endemic for malaria on account of waterlogging and seepage in the canal
catchment area. There are also numerous cases of filariases in various irrigation commands
(FAO 2002). Furthermore, irrigation projects tend to substantially alter the local
environment that has resulted in the spread of new diseases like schistosomiasis,
dracunculiasis, etc. The prevalence of water borne diseases like Guinea worm in the
command area of Uppcr Krishna Project is attributed to the impoundment and stagnation of
water.
It is well known that in waterlogged and saline areas agricultural yield decreases. Farmers,
therefore, try to use excessive fertilizers and pesticides to increase yield. Those fertilizers
release toxin-elemcnts into the environment. It is estimated that only 0.1 percent of applied
pesticides reach the target pests, leaving the bulk of the pesticides (99.9 percent) to impact
the environment (Pimental 1995). Scientists have linked alarming discoveries of death and
reproductive failure in fish, birds and other wild life to agriculture drainage water laced
with toxic chemicals. In addition to pesticides, leaching of fertilizer salts from agricultural
land is also linked to groundwater pollution, espccially nitrate pollution with signi ficant
impacts on human health 6 . Salt-affected soils can also have indirect human health impacts
6 A study conducted by Gumtang et al. (1999) in the intensive rice cropping systems in the !locos Norte
region of the Philippines found that thc use of nitrogen tertilizer had resulted in well water contamination
such that the nitrate· nitrogen in R out of 19 wells in the study area were close to or exceeded the WHO
recommended limit for drinking water.
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