A New Approach to Calculate the Water Exploitation Index (WEI+)

The Water Exploitation Index (WEI), or withdrawal ratio, is an indicator of water scarcity, which has been updated into its WEI+ form by the Committee of Experts of the European Commission. In calculating the total abstraction of fresh water, this indicator also includes the possible return flow and management rules. The demand for freshwater and long-term freshwater resources are both necessary to calculate the WEI+. These values are not easy to assess at basin or sub-basin level and, for this reason, WEI values are generally calculated at the country level. This paper introduces a new approach to calculate the WEI+, with the purpose of extending its use to basin and sub-basin levels. The methodology is based on flow duration curve estimation, which evaluates freshwater resources, and a Web-GIS system that evaluates water abstractions distribution. This approach allows for the assessment of locally stressed areas in the hydrographic network and could provide a fundamental step toward more comprehensive regional water resources management plans. The new methodology is tested in some sub-basins of the Upper Tiber River Basin (Italy). These results contribute to the analysis of water withdrawals sustainability, based on the policy of the European Environment Agency, which is aimed toward the development of a proactive approach for reducing water stress.

CENÁRIO TENDENCIAL DE COMPROMETIMENTO HÍDRICO NA BACIA HIDROGRÁFICA DO RIO SÃO MATEUS - ES

Nesse estudo analisou-se o cenário tendencial do comprometimento hídrico na porção capixaba da bacia hidrográfica do rio São Mateus, norte do Espírito Santo. Para isso foi estimada a disponibilidade hídrica da bacia a partir de equações de regionalização e foram levantadas as demandas hídricas dos seus principais setores usuários de água. Para análise do comprometimento hídrico utilizou-se o índice Water Exploitation Index (WEI). Como resultado, verificou-se uma predominância do uso de água com fins de irrigação em toda a bacia, cujo percentual de uso alcançou valores da ordem de 98% nas porções média e alta da bacia. Quanto ao índice WEI, observou-se atualmente uma situação preocupante em determinadas porções da bacia, com 17,4% da disponibilidade hídrica já comprometida com as atuais demandas. A tendência para o horizonte de 20 anos será de agravamento do comprometimento hídrico, com essa relação chegando a 20,5%. Diante o cenário exposto, identificaram-se áreas prioritárias para investimento em medidas de gerenciamento da demanda dos recursos hídricos, principalmente para o setor de irrigação, indicando a necessidade de utilização de técnicas mais eficientes do uso da água e da adoção de outros instrumentos de gestão, como a outorga coletiva, de forma a alcançar a sustentabilidade hídrica da bacia.

Balancing exploitation and conservation of the eastern Scotian Shelf ecosystem: application of a 4D ecosystem exploitation index

Few indicators exist that measure the effects of fishing at the whole-ecosystem level. A 4D ecosystem exploitation index is proposed that integrates four measures of ecosystem status: (i) the trophic balance of exploitation, (ii) the intensity of exploitation, (iii) species richness, and (iv) disturbance of the trophic structure. The central concept is that fisheries should extract yield in proportion to the productivity at each trophic level, at sustainable exploitation rates, with minimal disturbance to the trophic structure, and with no loss in species richness. The ecosystem exploitation index is tested on simulated ecosystem data and applied to data from the eastern Scotian Shelf, Canada. The model simulations provided consistent results that should facilitate cross-system comparisons of exploitation and ecosystem status. When applied to actual observations, the results were less coherent, likely attributable to lag effects and environmental impacts. All fisheries likely alter the trophic structure of ecosystems, and the rate and trophic pattern of exploitation determines the level of change. Exploiting all trophic levels equally would always result in less change to trophic structure than top-heavy exploitation. Further testing is required to determine lag effects and sensitivity to various assumptions.