EARTH SCIENCE: Salt and Sustainability

Science  28 Oct 2005:
Vol. 310, Issue 5748, pp. 593a
DOI: 10.1126/science.310.5748.593a

Agriculture in many semi-arid areas of the world requires irrigation—from either stored snowmelt or groundwater. High evaporation rates in turn lead to the accumulation of salts in the soil that hinder productivity and can degrade water quality downstream and, over time, potentially in groundwater. Salination of soils is affecting critical agricultural areas such as the Nile Delta and central California. Schoups et al. present a model of the hydrologic history of the San Joaquin Valley, California, that accounts for the salt deposition in soil, the salinity of surface-and groundwater, and the history of water use during the past 60 years. By including information about the shifts in irrigation sources and about extreme droughts, the model accurately predicts the local distribution of salt in the San Joaquin soils. Although the amount of salt in the soils has held steady recently, the model suggests that recharge waters moving through these deposits are increasing the salinity even of deep aquifers, and will likely continue to do so, posing a major problem for the sustainability of agriculture in this region. — BH

Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.0507723102 (2005).

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