Comparison between water scarcity indices and detailed water accounts for the elaboration of River Basin Water Management Plans

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Fernando Pereira, Stef Michielsen, Renaat De Sutter

Thursday 2 july 2015

14:35 - 14:50h at Oceania Foyer (level 0)

Themes: (T) Water resources and hydro informatics (WRHI), (ST) Surface and subsurface flow interactions

Parallel session: 12L. Water resources - Flow interactions

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Water scarcity is a human induced phenomenon. The overuse of water resources causes an imbalance because the need for water is significantly higher than the renewable availability. During past decennia, many indices have been developed to quantify nations water resources vulnerability. Typically, such indices are based on (long-term) yearly (averaged) data, on a national or regional level and give a more general idea of the state a nation is at. Therefore, minds are shifting towards water balances or water accounts to express the vulnerability for water stress on a smaller time scale and on a basin level. Water balances can support in the development of river basin management plans by identifying the pressures on the water availability and their impact. The European commission is hence preparing a guidance document on water balances to evaluate water scarcity instead of the Water Exploitation Index (plus) hitherto used. The Scheldt River basin (> 20 000 km²) has been conceptualized in a detailed water balance model taking into account all major water users. This instrument can simulate a 40 years long historical period using the actual water consumption, on a daily basis. Such instruments are suitable for detecting which sectors experience shortages, under which conditions and to what extent. It has been used to quantify the impact of new water users, to analyze the impact of new locks, to assess the environmental surface water quantity goals, to study the impact of climate change on water availability…. Based on the results, water shortages are identified and analyzed in terms of frequency, duration and this for each sector and different locations. These results are compared to the results of the WEI and the possible consequences to the elaboration of river basin management plans are discussed. Flanders now has a tool with which it is able to identify shortages on a local scale and on a daily time basis. It allows water managers to take specific actions and can raise stakeholders awareness for their vulnerability towards shortages, now and in the future.