Global synthesis of groundwater recharge in semiarid and arid regions

• DOI: 10.1002/hyp.6335
• Publication Date: 2006-09-25T11:56:12Z
• Authors: Bridget R. Scanlon; Kelley E. Keese; Alan L. Flint; Lorraine E. Flint; Cheikh B. Gaye; W. Michael Edmunds; Ian Simmers
• Keywords: Water balance

Abstract Global synthesis of the findings from ∼140 recharge study areas in semiarid and arid regions provides important information on rates, controls, processes, which are critical for sustainable water development. Water resource evaluation, dryland salinity assessment (Australia), radioactive waste disposal (US) among primary goals many these studies. The chloride mass balance (CMB) technique is widely used to estimate recharge. Average rates estimated over large (40–374 000 km 2 ) range 0·2 35 mm year −1 , representing 0·1–5% long‐term average annual precipitation. Extreme local variability recharge, with up ∼720 m results focussed beneath ephemeral streams lakes preferential flow mostly fractured systems. System response climate land use/land cover (LU/LC) changes archived unsaturated zone tracer profiles groundwater level fluctuations. Inter‐annual related El Niño Southern Oscillation (ENSO) three times higher within SW US during periods frequent Niños (1977–1998) relative dominated by La Niñas (1941–1957). Enhanced ENSO also documented Argentina. Climate at decadal century scales recorded Africa 30 Sahel drought (1970–1986) 150 non‐drought periods. Variations millennial changed systems Pleistocene glacial period (≥10 years ago) discharge Holocene period. LU/LC such as deforestation Australia increased about orders magnitude. Changes natural grassland shrublands (rain‐fed) agriculture altered (evapotranspiration, ET) US. impact LU change was much greater than Niger (Africa), where replacement savanna crops an order magnitude even severe droughts. Sensitivity suggests that may be controlled through management LU. In irrigated areas, varies 10 485 1–25% irrigation plus However, pumpage groundwater‐fed greatly exceeds resulting mining. Increased cultivation has mobilized salts accumulated millennia, widespread surface contamination, particularly Australia. provided this contains valuable developing programmes context change. Copyright © 2006 John Wiley & Sons, Ltd.