Reservoir operating policies for irrigation districts in Mexico

The National Water Commission has a clear policy for operating reservoirs, which are the main source of water for the irrigation districts, to minimize spills. Unfortunately it has not a similar policy to avoid the drying up of the dams, even if the economic and social negative impacts could be greater than those produced by spills. In fact, since 1993 when most of the irrigation districts were transferred to the Water Users Associations the total water storage in those reservoirs has shown a tendency to diminish. Twice during the previous years the levels of storage have reached minimum values, and perhaps in 1999 these values could be smaller To assess the social and economic impact of drying the dams, an example is shown, using information from the Lagunera region, where in 1996 only one third of the district area was irrigated, due to the little water available in the two dams. This situation was the result of the water withdrawsals in the previous years, greater than the volume recommended by a Presidential decree of 1988. In this paper, using data from the Lagunera region, the economic and social negative effects of water withdrawal upon the average annual water available, are shown.