Assessing the long-term impact of climatic variability and human activities on the water resources of a meso-scale Mediterranean catchment

Abstract

long-term impact of climatic variability and human activities on the water resources of a meso-scale Mediterranean catchment. Hydrological Sciences Journal, 59 (8), 1457-1469. http://dx.doi.org/10. 1080/02626667.2013.842073 Abstract This article addresses the critical need for a better quantitative understanding of how water resources from the Hérault River catchment in France have been influenced by climate variability and the increasing pressure of human activity over the last 50 years. A method is proposed for assessing the relative impacts of climate and growing water demand on the decrease in discharge observed at various gauging stations in the periods 1961-1980 and 1981-2010. An annual water balance at the basin scale was calculated first, taking into account precipitation, actual evapotranspiration, water withdrawals and water discharge. Next, the evolution of the seasonal variability in hydroclimatic conditions and water withdrawals was studied. The catchment was then divided into zones according to the main geographical characteristics to investigate the heterogeneity of the climatic and human dynamics. This delimitation took into account the distribution of climate, topography, lithology, land cover and water uses, as well as the availability of discharge series. At the area scale, annual water balances were calculated to understand the internal changes that occurred in the catchment between both past periods. The decrease in runoff can be explained by the decrease in winter precipitation in the upstream areas and by the increase during summer in both water withdrawals and evapotranspiration in the downstream areas, mainly due to the increase in temperature. Thus, water stress increased in summer by 35%. This work is the first step of a larger research project to assess possible future changes in the capacity to satisfy water demand in the Hérault River catchment, using a model that combines hydrological processes and water demand.Key words climate variability; long-term impact; water balance; water use; Mediterranean catchment Evaluation sur le long terme de l'impact de la variabilité climatique et des activités humaines sur les ressources en eau d'un bassin Méditerranéen de méso-échelle Résumé Cet article vise à mieux comprendre l'impact relatif de la variabilité climatique et de l'augmentation des pressions anthropiques sur l'évolution des ressources en eau du bassin de l'Hérault au cours des 50 dernières années. Une méthode est proposée pour évaluer cet impact sur la diminution observée des écoulements en plusieurs stations de jaugeage entre les périodes 1961-1980 et 1981-2010. Un bilan hydrologique annuel a tout d'abord été calculé, en tenant compte de la précipitation, de l'évapotranspiration réelle, des prélèvements en eau et du débit. Ensuite, l'évolution de la variabilité saisonnière des conditions hydro-climatiques et des prélèvements en eau a été étudiée. Le bassin a ensuite été divisé en plusieurs biefs selon les caractéristiques géographiques principales pour comprendre l'hétérogénéité...

Simulating past changes in the balance between water demand and availability and assessing their main drivers at the river basin scale

“…Seasonal disparities were identified in the precipitation trends: while winter precipitation decreased by approximately 40 % between the two periods in both basins, fall precipitation increased by 21 % over the Hérault Basin and by 12 % over the Ebro Basin. Similar hydro-climatic trends were detected by Collet et al (2014) and Milano et al (2013aMilano et al ( ) in the 1969Milano et al ( -2010Milano et al ( and 1957Milano et al ( -2002 periods in the Hérault and Ebro basins, respectively. Figure 1 shows the main anthropogenic pressures on water resources in the Hérault and the Ebro Basins.…”

Water supply sustainability and adaptation strategies under anthropogenic and climatic changes of a meso-scale Mediterranean catchment

“…The temperature is highest in summer and lowest in winter. As described by Collet et al (2014), the upstream part of the catchment contributes the greatest precipitation and has the lowest temperatures while the downstream part has the least precipitation and the highest temperatures.…”

“…1). This delineation was previously shown to be suitable for studies of water resources management over a long time period in this catchment (Collet et al, 2014). It accounts for the different hydroclimatic processes within the catchment as well as for the main water demand sites and river discharge regulations by the main storage dam (see Fig.…”

Historical reconstruction and 2050 projections of water demand under anthropogenic and climate changes in two contrasted Mediterranean catchments

“…de Graaf et al, 2004;Beck and Bernauer, 2011;Collet et al, 2014;Dawadi and Ahmad, 2013;Milano et al, 2013b;Hejazi et al, 2014). Three main issues were identified in these studies: (i) water demand is not always considered as a whole i.e., not all its components (agricultural, urban, industrial, energy) are accounted for; (ii) spatialization of data is not always consistent with the goals of connection with water supply assessment; and (iii) the reduced time depths and large time steps usually used, do not accurately account for the temporal variability of the drivers of water demand.…”