Groundwater–Surface Water Interaction: Process Understanding, Conceptualization and Modelling (Proceedings of Symposium HS1002 at IUGG2007, Perugia, July 2007). IAHS Publ. 321, 2008, 197-203.

Effect of an irrigation canal network on surface and groundwater connections in an agricultural valley in Central Chile

JOSE LUIS ARUMI¹, DIEGO RIVERA¹, EDUARDO HOLZAPFEL¹ & ALEXANDER FERNALD²

1 University of Concepción, Department of Water Resources, Vicente Mendez 595, Chillan, Chile

jarumi@udec.cl

2 New Mexico State University, Department of Animal and Range Sciences, PO Box 30003, MSC 3-I, Las Cruces,
New Mexico, USA

Abstract Agricultural production of high value crops in Chile’s Central Valley is highly dependent on surface water and groundwater, where interactions between the two are likely. Yet hydrological processes in the valley have not been well documented. This research addressed two study questions: (1) What is the effect of irrigation canal seepage on groundwater recharge; and (2) What are the within-valley spatial patterns of river–aquifer interactions. This study was undertaken from 2003 to 2007 in the Peumo Valley in Central Chile. Water levels rose after the onset of the irrigation season associated with irrigation canal seepage. The spatial relationship between river stage and valley shallow aquifer changed from an effluent river at the head of the valley to an influent river at the bottom of the valley. Hydrological limitations on agricultural production in similar areas can be overcome by a system-wide appreciation of the interactions between surface water and groundwater.

Key words agriculture; Chile; groundwater; irrigation seepage; MODFLOW; surface water–groundwater interactions