Sustainable Water Management under Climate Change

Water, that is often the main limiting factor of plant growth, is also the main factor directly or indirectly responsible for soil and land degradation processes. These processes affect the conservation of the increasingly scarce soil and water resources, because they are strongly linked to unfavorable changes in the hydrological behavior affecting soil water balance and soil moisture regime. They are related to soil and climate characteristics, but inappropriate land use and soil and water management are the main factors responsible of those processes. The previewed effects of global climate changes would mainly affect hydrological processes in the land surface mostly related to the soil water balance. Soil water management, both under dry-land and irrigated conditions, may affect more the soil hydrological processes than the previewed climate changes, or may increase the influence of those changes on soil degradation processes. In any case it is important to include the effects of climate change in the performance of current or planned water management systems. Weak knowledge of the hydrological processes involved, generally associated to the inadequacy of methods for assessing and monitoring such processes, including the use of pedo-transfer functions, has usually hampered the adoption of adequate integral soil and water management policies for prediction and prevention of soil and water degradation of soil and water resources in situ and related effects like surface and groundwater contamination, droughts, flooding, landslides, sedimentation, etc. To avoid these failures there would be required non empirical modeling approaches, mainly based on soil hydrological processes together with rainfall records, under different scenarios of changing climate, soil properties, topography, and land use and water management. Simulation models based on hydrological processes allow to integrate and to convert the measured or estimated soil, climate and management parameters into predicted soil water balances and soil moisture regimes for each particular combination, actual or previewed, of them. Those models must allow to incorporate potentially significant and highly uncertain information about potential climate change. Such approach has been applied to the evaluation of the effects on the soil water balance and soil moisture regime, associated to new land and crop management systems, and to the previewed climate changes, in dry-land and irrigated vineyards for quality wine production in NE Spain. The generated information has been used in planning strategies for land use, and in the selection of the soil and water management practices, based on probabilities of success, levels of risk and long term sustainability. Special attention is given to the water use efficiency, under the semiarid Mediterranean climate, with low and very variable and erratic rainfall, and with scarce availability of water for irrigation, in relation to the production, both in quantity and quality of grapevines and wine. The management strategies may be evaluated against different scenarios of changing climate conditions, taking decisions after assigning probabilities to each scenario and weighting the results.