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Title: A ROOT ZONE MODELLING APPROACH TO ESTIMATING GROUNDWATER RECHARGE FROM IRRIGATED AREAS

Author
item JIMENEZ-MARTINEZ, J - TECH UNIV, SPAIN
item Skaggs, Todd
item VAN GENUCHTEN, MARTINUS - UNIV RIO DE JANEIRO
item CANDELA, L - TECH UNIV, SAPIN

Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2009
Publication Date: 3/30/2009
Citation: Jimenez-Martinez, J., Skaggs, T.H., Van Genuchten, M.T., Candela, L. 2009. A Root Zone Modelling Approach to Estimating Ground Recharge from Irrigated Areas. Journal of Hydrology. 367:138–149.

Interpretive Summary: Groundwater recharge is the hydrologic process by which water moves from the land surface down to the water table. Accurate knowledge of groundwater recharge rates is important for the sustainable management of water resources. Estimating recharge rates is difficult in arid and semi-arid regions where water tables are deep and recharge is predominately “focused recharge” that emanates from topological depressions such as streams and lakes. In some basins, recharge is additionally complicated by irrigation, which may simultaneously remove water from focused recharge sources while creating new sources of diffuse recharge. In this study, we investigated a computer modelling approach to calculating the recharge that results from irrigation in semi-arid basins. As an example, we estimated recharge for the Campo de Cartagena area of southeast Spain, a semi-arid region where irrigation return flow accounts for a substantial portion of recharge. Our calculations indicated that irrigation of annual fruits and vegetables produces 26 hm3 y-1 of groundwater recharge in the Campo de Cartagena plain, an amount that is larger than previously estimated. This research will help hydrologists and engineers quantify groundwater recharge and develop science-based guidelines for sustainable water management.

Technical Abstract: In irrigated semi-arid and arid regions, accurate knowledge of groundwater recharge is important for the sustainable management of scarce water resources. The Campo de Cartagena area of southeast Spain is a semi-arid region where irrigation return flow accounts for a substantial portion of recharge. In this study we estimated irrigation return flow using a root zone modelling approach in which irrigation, evapotranspiration, and soil moisture dynamics for specific crops and irrigation regimes were simulated with the HYDRUS-1D software package. The model was calibrated using field data collected in an experimental plot. Good agreement was achieved between the HYDRUS-1D simulations and field measurements made under melon and lettuce crops. The simulations indicated that water use by the crops was below potential levels despite regular irrigation. The fraction of applied water (irrigation plus precipitation) going to recharge ranged from 22 percent for a summer melon crop to 68 percent for a fall lettuce crop. In total, we estimate that irrigation of annual fruits and vegetables produces 26 hm3 y-1 of groundwater recharge in the area. This estimate does not include important irrigated perennial crops in the region, such as artichoke and citrus. Overall, the results suggest a greater amount of irrigation return flow in the Campo de Cartagena region than was previously estimated.