Strategies to Mitigate Secondary Salinization in the Indus Basin of Pakistan: A Selective Review

Abstract

"The Indus Basin Irrigation System (IBIS) of Pakistan serves an area of 16 million hectares (Mha) and distributes 172 billion cubic meters (BCM) of river water per year. With the introduction of IBIS, groundwater levels rose at a rate of 15 to 75 cm per year. The capillary up-flow from shallow water tables and evapotranspiration concentrate the salt, which salanizes the soil and water. In areas where river water is unavailable and groundwater of marginal quality is used for irrigation, evapotranspiration leads to sodicity. Estimates of losses due to salinization are 28,000 to 40,000 ha of land and about US$230 million (PRs 14,000 million) of revenue per year. An area of about 2 Mha is estimated to be salinized at present.

"In response, researchers, policymakers, agency personnel and farmers in Pakistan have continuously devised strategies to mitigate secondary salinization. These can be categorized into on-farm and off-farm strategies. On-farm strategies include: (a) improved irrigation practices; (b) deficit irrigation; (c) change in land use; (d) agroforestry and biological-drainage; (e) mechanical cultivation; (f) use of chemical amendments; (g) use of skimming wells for irrigation water; and (h) conjunctive water use. Off-farm strategies include: (a) participatory irrigation system management; (b) improving reliability of canal water; (c) selective maintenance of irrigation and drainage infrastructure; (d) revision of water allocation rules currently in place; and (e) drainage measures at sub-regional and regional levels.

"This report discusses the nature and causes of secondary salinization, reviews strategies developed and tested within IBIS to mitigate salinization, and identifies areas requiring further investigation."