Strategies for regional-scale recovery of a salinity-threatened irrigated river valley

Abstract

Two major problems that inherently stem from irrigation practice threaten the vitality of many of today's agricultural regions. Salinity of soils and irrigation water and waterlogging of fields due to high water tables have caused significant adverse socio-economic and large-scale environmental problems worldwide. Currently, at least one-fifth of the total irrigated land in the world is damaged by salinity build-up, and this damage translates to an estimated US$11 billion in reduced farmer income (Postel 1999). In the study presented, an area comprising 26,400 irrigated hectares (65,300 ac) located within the Lower Arkansas River Valley of Colorado, was investigated through intensive data collection over a period of four years to quantify the current salinity and waterlogging crisis in the region. Additionally, utilizing the collected data, a three-dimensional, transient, finite-difference groundwater model was developed, calibrated, and applied to evaluate alternative solution strategies. Considered strategies include improvements in on-farm irrigation practices, upgrading of the irrigation-water-delivery infrastructure (e.g. canal lining), and investment in new surface and sub-surface drainage facilities (e.g. use of pumping wells as vertical drains, installation of horizontal "tile" drains). Predicted effects on water table depth and salinity are presented and discussed.