ABSTRACT
Effect of the irrigation canal network on surface and groundwater interactions in the lower valley of the Cachapoal river, Chile

José Luis Arumí1*, Diego Rivera1, Eduardo Holzapfel1, Peter Boochs2, Max Billib2, and Alexander Fernald3
 
Agricultural production of high value crops in Chile's Central Valley is highly dependent on surface and groundwater resources. They are connected and together form an integrated hydrological system, the individual components of which have to be studied. This research is addressed to answering two questions: 1) to what extent do irrigation and canal seepage contribute to groundwater recharge and 2) what is the influence of the interactions between the Cachapoal River and ground water. The study was carried out from 2003 to 2007 in Peumo Valley (34.3° S, 71.3° W). In winter, the irrigation canal network intercepts and diverts surface runoff, which flows to flat areas and recharges groundwater. In summer, infiltration from the canals recharges the aquifer directly and partially compensates for water uptake from plants and evaporation. The effects of both interactions keep groundwater at a relatively constant level over the whole year. The water balance of the valley is strongly affected by agricultural practices, groundwater recharge mainly originating from irrigation loss (22%) and canal seepage (52%). It is important to know how management decisions, such as change in irrigation practices or canal lining, can affect the hydrological system and agricultural production within the valley.
Keywords: agriculture, Chile, groundwater, irrigation seepage, MODFLOW, surface water-groundwater interactions.
1 Universidad de Concepción, Facultad de Ingeniería Agrícola, Av. Vicente Mendez 595, Chillán, Chile. *Corresponding author (jarumi@udec.cl )
2 University of Hannover, Institute of Water Resources Management, Hydrology and Agricultural Hydraulic Engineering (WAWI), Leibniz, Appelstr. 9A, 30167, Hannover, Germany.
3 New Mexico State University, Department of Animal and Range Sciences, PO Box 30003, MSC 3-I, Las Cruces, New Mexico, USA.