Regional environmental assessment of the impacts of large dams in Mexico

Mexico's Ministry of Environment has commissioned a research program for the Santiago river basin to evaluate the cumulative environmental impacts of at least five hydro dams built several decades ago. More than 50 years ago, several dams for water supply, irrigation and hydropower generation were built on the Santiago river, without the designation of an environmental influence area. The Santiago river, in northwest Mexico, has an annual average runoff of 7850 x 106 m3 and a catchment area of approximately 77 185 km2. The main objective of the regional study is to evaluate the cumulative, synergistic and residual impacts resulting from at least five of the major hydro schemes on the Santiago River. Damming the Santiago River has followed a national policy compatible with meeting energy demands in the country and encouraging economic development. Recently, the consideration of damming rivers already harnessed, instead of pristine ones, has contributed to the authorization of building new dams on the river.