Management issues arising from intensive groundwater use

CHAMBOULEYRON, J.; SALATINO, S.; DROVANDI, A.; MEDINA, R.; ZIMERMMANN, M.; MARRE, M.; BUSTOS, R.; ANTONIOLLI, M.; FILIPPINI, M.; NACIF, N.; CAMPOS, S.; DEDIOL, C.; CAMARGO, A.; GENOVESE, D.

Madrid - España

Congreso; XI World Water Congress. Water Resources Management in the 21st Century; 2003

The paper describes an innovative approach to the hydrological dynamics of the irrigated area by the River Tunuyán in the central piedmont oasis in the Province of Mendoza (Argentina). The area is divided into two sub-basins (upper and lower, with 54,000 and 81,000 ha, respectively, with registered irrigation rights) administered by two Sub-delegations of the General Department of Irrigation (DGI). The explosive growth that took place in the upper  basin in the 1990s -planting of quality grapevines for wines destined to the international market and irrigated solely with groundwater using pressurized irrigation- has made it possible to project a significant degradation in the quality of water reaching the Lower Tunuyán basin.  Thus, pumping a flow to meet the needs of 20,000 ha planted with vineyards (200 Hm3) will reduce the flow of the many brooks and streams rising in the upper basin. They would become mere drainage collectors conveying very low quality, water (high salinity) to the lover basin and affecting crop yields. For a potential increase of 20,000 ha in the upper basin, estimates show a salt content increase in irrigation water from the present 1130 UScm-1 to some 1420 UScm-1 in the lower basin. This would diminish the available water supply, which may suffice to meet the requirements of only one third of the registered area, and would substantially reduce crop yields (grapes and peaches) between 12 and 22%. All this poses a challenge to water management both for the DGI and users´ organizations ("Canal inspections"). For a modern, sustainable and integrated surface and groundwater management, with no disruption of the basin´s ecosystem balance, it is recommended that the structural and non-structural factors of the complex mechanism of variables interrelation be taken into account. Users´ organizations should also be involved in the process, attain economies of scale and become financially self-sufficient. It is further recommended that water management be consolidated at basin level; that water be distributed in a proportional and equitable manner on the basis of quality and salt content -as is the case of the Murray-Darling Basin in Australia and the River Colorado in the Province of Mendoza-; and that  groundwater be integrated into water management, with users´ organizations  assuming responsibility for water  management and pollution control (decentralized administration).