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Title: ASSESSING WATER SHORTAGE RISK DUE TO DROUGHT IN COMPLEX WATER SYSTEMS UNDER CLIMATE CHANGE SCENARIOS

Author: G. Rossi, V. Nicolosi, V. Caruso and A. Cancelliere

Year: 2009

Publisher: European Water Resources Association (EWRA)

Description:

Impacts of climate-induced hydrological changes are expected to exacerbate the pressure on complex water supply systems located in drought-prone areas. A strategic approach to water resources management should take into account these impacts also by including the assessment of the risk of water shortages due to drought. The paper presents a pilot implementation of the shortage risk assessment method on which is based a Strategic Water Shortage Preparedness Plan for a complex water system supplying several competing uses taking into account either current conditions or hydrological scenarios consequent to potential changes in climate. The water system chosen as case study is a typical Mediterranean complex water supply system that strongly relies on surface water regulated through reservoirs. The water supply system has been simulated considering future configuration of hydraulic infrastructures, reduced water availability at the river sections due to the impacts of climate change and measures to mitigate drought impacts. The considered scenario has been
developed taking into account the assessment carried out by the three Working Groups (WGs) of the Intergovernmental Panel on Climate Change (IPCC) and the IPCC’s Fourth Assessment Report (AR4) specifically tailored for considering local trends on observed data in temperatures and precipitations. A general decrease
on precipitation and increase on temperatures can be inferred from the observed 42 years time series with greater precipitation reduction for the JFM quarter. Precipitation reduction causes reduction in streamflows close to 30% in some extreme cases. The risk of water shortage due to drought has been analyzed both through traditional performance indices and the probability of shortages belonging to different classes expressed as a percentage of the monthly demand. This kind of representation of results gives clear and not-ambiguous information to water managers on the impacts of the specific climate change scenario and the effectiveness of the chosen mitigation measures. Analysis of results has been carried out also with reference to reduced demands obtained by fixing thresholds considered acceptable for the different uses.