RESUMO
PIP: The case of the Laja River basin in Mexico illustrates the argument that over exploitation of water resources must be analyzed in broader terms than mere population growth. The work begins with an examination of the persistence in Mexico of a Malthusian focus in works on the relationship between population growth and the carrying capacity of river basins. Theoretical focuses that include social, cultural, and economic characteristics as well as physical factors in definitions of environment assume a systemic perspective that makes possible examination of relations between regional social systems and natural systems. The Laja basin was selected for study because of its high degree of internal ecological diversity, wide variety of agricultural systems, and multiple conflicts over water use. In the past three decades, with introduction of deep well technology and policies to promote a cheap food supply, a dualist agricultural economy has developed in which large producers growing commercial and export crops coexist with subsistence farmers who have probably reduced their use of irrigation. The river basin is deteriorating due to over exploitation of all natural resources and rapid demographic growth stemming from regional industrialization. The region has arrived at critical limits in only a few years, with the local population little involved in the process. The case suggests that proposals to stem deterioration of water resources cannot rely solely on technical solutions, but must involve achievement of consensus between the parties involved.^ieng