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Water distribution networks are low-energy efficiency systems, due to the high energy consumption, as well as the large amount of water leakage, which are caused by high pressures in the networks. In this study, the optimal location of pumps as turbines (PATs) within a water distribution network is investigated in order to maximize the production of energy and water savings, as well as minimize installation costs. A literature mathematical model has been employed as reference model and the weaknesses of this previous study have been overcome by new constraints. The main preliminary results of the new optimization procedure will be presented and compared with the literature results. According to the results, the new optimization ensures a good solution, in term of water and energy savings, with low investment cost and a fast return in investment.

Summary The 1970s abrupt lake level rise of Laguna Mar Chiquita in central Argentina was shown to be driven by an increase in the Rio Sali-Dulce discharge outflowing from the northern part of the lake catchment. This regional hydrological change was consistent with the 20th century hydroclimatic trends observed in southeastern South America. However, little is known about the impacts of climate or land cover changes on this regional hydrological change causing the sharp lake level rise. To address this question, the present study aims to provide an integrated basin-lake model. We used the physically-based SWAT model in order to simulate streamflow in the Sali-Dulce Basin. The ability of SWAT to simulate non-stationary hydrological conditions was evaluated by a cross-calibration exercise. Based on observed daily meteorological data over 1973–2004, two successive 9-year periods referred to as wet (P1976–1985 = 1205 mm/yr) and dry (P1986–1995 = 796 mm/yr) periods were selected. The calibration yielded similar Nash–Sutcliffe efficiencies (NSE) at the monthly time scale for both periods (NSEwet = 0.86; NSEdry = 0.90) supporting the model’s ability to adapt its structure to changing climatic situations. The simulation was extended in scarce data conditions over 1931–1972 and the simulation of monthly discharge values was acceptable (NSE = 0.71). When precipitation in the model was increased until it reach the change observed in the 1970s ( Δ P / P ¯ = 22 % ), the resulting increase in streamflow was found to closely match the 1970s hydrological change ( Δ Q / Q ¯ = 45 % ). Sensitivity analyses revealed that the land cover changes had a minor impact on the 1970s hydrological changes in the Sali-Dulce Basin. Integrating the SWAT simulations within the lake model over 1973–2004 provided lake level variations similar to those obtained using observed discharge values. Over the longer period, going back to 1931, the main features of lake levels were still adequately reproduced, which suggests that this basin-lake model is a promising approach for simulating long-term lake level fluctuations in response to climate.

This paper addresses the conversion of narrow-to-broadband radiances in the special case of the sensor SEVIRI onboard the satellite Meteosat-8 of the Meteosat Second Generation (MSG). The advent of this new program poses the problem of the transfer of operational procedures from the previous satellite Meteosat-7 to MSG. Among these operational procedures are several different implementations of the Heliosat method to convert Meteosat data into irradiance maps. An easy-to-implement fast-running method is proposed that combines the radiances of the two narrow visible bands of SEVIRI to produce broadband radiances that are almost identical to those observed in the broadband channel of Meteosat-7. A comparison between Meteosat-7 actual radiances and these simulated-radiances shows errors with a negligible bias and a relative root mean square error (RMSE) of 6%. After combination with the uncertainties found in the calibration procedures (10-13%), the total relative RMSE on the radiances amounts to 12-14%. It is concluded that the Meteosat-8 images may be used in operational procedures currently applied to Meteosat-7 images.

The Semi-Arid Land-Surface-Atmosphere Program (SALSA) is a multi-agency, multi-national research effort that seeks to evaluate the consequences of natural and human-induced environmental change in semi-arid regions. The ultimate goal of SALSA is to advance scientific understanding of the semi-arid portion of the hydrosphere-biosphere interface in order to provide reliable information for environmental decision making. SALSA approaches this goal through a program of long-term, integrated observations, process research, modeling, assessment, and information management that is sustained by cooperation among scientists and information users. In this preface to the SALSA special issue, general program background information and the critical nature of semi-arid regions is presented. A brief description of the Upper San Pedro River Basin, the initial location for focused SALSA research follows. Several overarching research objectives under which much of the interdisciplinary research contained in the special issue was undertaken are discussed. Principal methods, primary research sites and data collection used by numerous investigators during 1997-1999 are then presented. Scientists from about 20 US, five European (four French and one Dutch), and three Mexican agencies and institutions have collaborated closely to make the research leading to this special issue a reality. The SALSA Program has served as a model of interagency cooperation by breaking new ground in the approach to large scale interdisciplinary science with relatively limited resources.

Projected changes in near-surface relative humidity (RH) remain highly model-dependent over land and may have been underestimated by the former generation global climate models. Here the focus in on the recent CNRM-CM6-1 model, which shows an enhanced land surface drying in response to quadrupled atmospheric CO2 compared to its CNRM-CM5 predecessor. Atmosphere-only experiments with prescribed sea surface temperature (SST) are used to decompose the simulated RH changes into separate responses to uniform SST warming, pattern of SST anomalies, changes in sea-ice concentration, as well as direct radiative and physiological CO2 effects. Results show that the strong drying simulated by CNRM-CM6-1 is due to both fast CO2 effects and a SST-mediated response. The enhanced drying compared to CNRM-CM5 is partly due to the introduction of the physiological CO2 effect that was not accounted for in CNRM-CM5. The global ocean warming also contributes to the RH decline over land, in reasonable agreement with the moisture advection mechanism proposed by earlier studies which however does not fully capture the contrasted RH response between the two CNRM models. The SST anomaly pattern is a significant driver of changes in RH humidity at the regional scale, which are partly explained by changes in atmospheric circulation. The improved land surface model may also contribute to a stronger soil moisture feedback in CNRM-CM6-1, which can amplify the surface aridity induced by global warming and, thereby, lead to a non-linear response of RH.

We investigate the interannual variability over 2003-2008 of different hydrological parameters in the Amazon river basin: (1) vertically-integrated water storage from the GRACE space gravimetry mission, (2) surface water level of the Amazon River and its tributaries from in situ gauge stations, and (3) precipitation. We analyze the spatio-temporal evolution of total water storage from GRACE and in situ river level along the Amazon River and its main tributaries and note significant differences between the various parts of the basin. We also perform an Empirical Orthogonal Decomposition of total water storage, river level and precipitation over the whole basin. We find that the 2003-2008 period, is characterized by two major hydrological events: a temporary drought in late 2005 that affected the western and central parts of the basin and very wet conditions peaking in mid-2006, in the eastern, northern and southern regions of the basin. Derivative of basin-average water storage from GRACE is shown to be highly correlated with the Southern Oscillation Index (a proxy of ENSO -- El Nino-Southern Oscillation), confirming that the spatio-temporal change in hydrology of the Amazon basin is at least partly driven by the ENSO phenomenon, as noticed in previous studies.