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Water Balance Components (water + balance_component)
Selected AbstractsEcohydrology of a semi-arid forest: partitioning among water balance components and its implications for predicted precipitation changesECOHYDROLOGY, Issue 2 2010Naama Raz Yaseef Abstract The distribution of precipitation inputs into different hydrological components of water-limited forest ecosystems determines water availability to trees and consequently forest productivity. We constructed a complete hydrological budget of a semi-arid pine forest (285 mm annual precipitation) by directly measuring its main components: precipitation (P), soil water content, evapotranspiration (ET, eddy covariance), tree transpiration (sap flux), soil evaporation (soil chambers), and intercepted precipitation (calculated). Our results indicated that on average for the 4-year study period, ET accounted for 94% of P, varying between 100% when P < 250 mm and 85% when P > 300 mm (with indications for losses to subsurface flow and soil moisture storage in wetter years). Direct measurements of the components of the ET flux demonstrated that both transpiration and soil evaporation were significant in this dry forest (45% and 36% of ET, respectively). Comparison between ecosystem ET (eddy covariance measurements) and the sum of its measured components showed good agreement on annual scales, but up to 30% discrepancies (in both directions) on shorter timescales. The pulsed storm pattern, characteristics of semi-arid climates, was sufficient to maintain the topsoil layer wet during the whole wet season. Only less often and intensive storms resulted in infiltration to the root zone, increasing water availability for uptake by deeper roots. Our results indicate that climate change predictions that link reduced precipitation with increased storm intensity may have a smaller effect on water availability to forest ecosystems than reduced precipitation alone, which could help forests' survival and maintain productivity even under drier conditions. Copyright © 2009 John Wiley & Sons, Ltd. [source] Assessing the results of scenarios of climate and land use changes on the hydrology of an Italian catchment: modelling studyHYDROLOGICAL PROCESSES, Issue 19 2010Daniela R. D'Agostino Abstract Hydrological models are recognized as valid scientific tools to study water quantity and quality and provide support for the integrated management and planning of water resources at different scales. In common with many catchments in the Mediterranean, the study catchment has many problems such as the increasing gap between water demand and supply, water quality deterioration, scarcity of available data, lack of measurements and specific information. The application of hydrological models to investigate hydrological processes in this type of catchments is of particular relevance for water planning strategies to address the possible impact of climate and land use changes on water resources. The distributed catchment scale model (DiCaSM) was selected to study the impact of climate and land use changes on the hydrological cycle and the water balance components in the Apulia region, southern Italy, specifically in the Candelaro catchment (1780 km2). The results obtained from this investigation proved the ability of DiCaSM to quantify the different components of the catchment water balance and to successfully simulate the stream flows. In addition, the model was run with the climate change scenarios for southern Italy, i.e. reduced winter rainfall by 5,10%, reduced summer rainfall by 15,20%, winter temperature rise by 1·25,1·5 °C and summer temperature rise by 1·5,1·75 °C. The results indicated that by 2050, groundwater recharge in the Candelaro catchment would decrease by 21,31% and stream flows by 16,23%. The model results also showed that the projected durum wheat yield up to 2050 is likely to decrease between 2·2% and 10·4% due to the future reduction in rainfall and increase in temperature. In the current study, the reliability of the DiCaSM was assessed when applied to the Candelaro catchment; those parameters that may cause uncertainty in model output were investigated using a generalized likelihood uncertainty estimation (GLUE) methodology. The results showed that DiCaSM provided a small level of uncertainty and subsequently, a higher confidence level. Copyright © 2010 John Wiley & Sons, Ltd. [source] Comparison of seven models for estimation of evapotranspiration and groundwater recharge using lysimeter measurement data in GermanyHYDROLOGICAL PROCESSES, Issue 18 2005C.-Y. Xu Abstract This study evaluates seven evapotranspiration models and their performance in water balance studies by using lysimeter measurement data at the Mönchengladbach hydrological and meteorological station in Germany. Of the seven evapotranspiration models evaluated, three models calculate actual evapotranspiration directly using the complementary relationship approach, i.e. the CRAE model of Morton, the advection,aridity (AA) model of Brutsaert and Stricker, and the GG model of Granger and Gray, and four models calculate first potential evapotranspiration and then actual evapotranspiration by considering the soil moisture condition. Two of the four potential evapotranspiration models belong to the temperature-based category, i.e. the Thornthwaite model and the Hargreaves model, and the other two belong to the radiation-based category, i.e. the Makkink model and the Priestley,Taylor model. The evapotranspiration calculated by the above seven models, together with precipitation, is used in the water balance model to calculate other water balance components. The results show that, for the calculation of actual evapotranspiration, the GG model and the Makkink model performed better than the other models; for the calculation of groundwater recharge using the water balance approach, the GG model and the AA models performed better; for the simulation of soil moisture content using the water balance approach, four models (GG, Thornthwaite, Makkink and Priestley,Taylor) out of the seven give equally good results. It can be concluded that the lysimeter-measured water balance components, i.e. actual evapotranspiration, groundwater recharge, soil moisture, etc., can be predicted by the GG model and the Makkink model with good accuracy. Copyright © 2005 John Wiley & Sons, Ltd. [source] Development of the ecohydrological model SWIM for regional impact studies and vulnerability assessmentHYDROLOGICAL PROCESSES, Issue 3 2005Valentina Krysanova Abstract In this paper the ecohydrological model SWIM developed for regional impact assessment is presented, and examples of approaches to climate and land use change impact studies are described. SWIM is a continuous-time semi-distributed ecohydrological model, integrating hydrological processes, vegetation, nutrients (nitrogen and phosphorus) and sediment transport at the river basin scale. Its spatial disaggregation scheme has three levels: (1) basin, (2) sub-basins and (3) hydrotopes within sub-basins. The model was extensively tested and validated for hydrological processes, nitrogen dynamics, crop yield and erosion (mainly in mesoscale sub-basins of the German part of the Elbe River basin). After appropriate validation in representative sub-basins, the model can be applied at the regional scale for impact studies. Particular interest in the global change impact studies is given to effects of expected changes in climate and land use on hydrological processes and agro-ecosystems, including water balance components, water quality and crop yield. This paper (a) introduces the reader to the class of process-based ecohydrological catchment scale models, (b) introduces SWIM as one such model, and (c) presents two examples of impact studies performed with SWIM for the federal state of Brandenburg (Germany), which overlaps with the lowland part of the Elbe drainage area. The impact studies provide a better understanding of the complex interactions between climate, hydrological processes and vegetation, and improve our potential adaptation to the expected changes. Copyright © 2005 John Wiley & Sons, Ltd. [source] Daily streamflow modelling and assessment based on the curve-number techniqueHYDROLOGICAL PROCESSES, Issue 16 2002Jin-Yong Choi Abstract A cell-based long-term hydrological model (CELTHYM) that can be integrated with a geographical information system (GIS) was developed to predict continuous stream flow from small agricultural watersheds. The CELTHYM uses a cell-by-cell soil moisture balance approach. For surface runoff estimation, the curve number technique considering soil moisture on a daily basis was used, and release rate was used to estimate baseflow. Evapotranspiration was computed using the FAO modified Penman equation that considered land-use-based crop coefficients, soil moisture and the influence of topography on radiation. A rice paddy field water budget model was also adapted for the specific application of the model to East Asia. Model sensitivity analysis was conducted to obtain operational information about the model calibration parameters. The CELTHYM was calibrated and verified with measured runoff data from the WS#1 and WS#3 watersheds of the Seoul National University, Department of Agricultural Engineering, in Hwaseong County, Kyounggi Province, South Korea. The WS#1 watershed is comprised of about 35·4% rice paddy fields and 42·3% forest, whereas the WS#3 watershed is about 85·0% forest and 11·5% rice paddy fields. The CELTHYM was calibrated for the parameter release rate, K, and soil moisture storage coefficient, STC, and results were compared with the measured runoff data for 1986. The validation results for WS#1 considering all daily stream flow were poor with R2, E2 and RMSE having values of 0·40, ,6·63 and 9·69 (mm), respectively, but validation results for days without rainfall were statistically significant (R2 = 0·66). Results for WS#3 showed good agreement with observed data for all days, and R2, E2 and RMSE were 0·92, 0·91 and 2·23 (mm), respectively, suggesting potential for CELTHYM application to other watersheds. The direct runoff and water balance components for watershed WS#1 with significant areas of paddy fields did not perform well, suggesting that additional study of these components is needed. Copyright © 2002 John Wiley & Sons, Ltd. [source] Canadian RCM projected climate-change signal and its sensitivity to model errorsINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 15 2006L. Sushama Abstract Climate change is commonly evaluated as the difference between simulated climates under future and current forcings, based on the assumption that systematic errors in the current-climate simulation do not affect the climate-change signal. In this paper, we investigate the Canadian Regional Climate Model (CRCM) projected climate changes in the climatological means and extremes of selected basin-scale surface fields and its sensitivity to model errors for Fraser, Mackenzie, Yukon, Nelson, Churchill and Mississippi basins, covering the major climate regions in North America, using current (1961,1990) and future climate simulations (2041,2070; A2 and IS92a scenarios) performed with two versions of CRCM. Assessment of errors in both model versions suggests the presence of nonnegligible biases in the surface fields, due primarily to the internal dynamics and physics of the regional model and to the errors in the driving data at the boundaries. In general, results demonstrate that, in spite of the errors in the two model versions, the simulated climate-change signals associated with the long-term monthly climatology of various surface water balance components (such as precipitation, evaporation, snow water equivalent (SWE), runoff and soil moisture) are consistent in sign, but differ in magnitude. The same is found for projected changes to the low-flow characteristics (frequency, timing and return levels) studied here. High-flow characteristics, particularly the seasonal distribution and return levels, appear to be more sensitive to the model version. CRCM climate-change projections indicate an increase in the average annual precipitation for all basins except Mississippi, while annual runoff increases in Fraser, Mackenzie and Yukon basins. A decrease in runoff is projected for Mississippi. A significant decrease in snow cover is projected for all basins, with maximum decrease in Fraser. Significant changes are also noted in the frequency, timing and return levels for low flows. Copyright © 2006 Royal Meteorological Society. [source] Modelling natural conditions and impacts of consumptive water use and sedimentation of Lake Abaya and Lake Chamo, EthiopiaLAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 2 2006Seleshi Bekele Awulachew Abstract There is few available information regarding the water resource systems of Abaya Lake and Chamo Lake, which are found in the Southern Rift Valley Region of Ethiopia. This paper describes modelling of the water balance components of these lakes, as well as the impacts of water uses, and sediment transport and deposition in the lakes. The various parameters and data needed for the water balance model are derived on the basis of various surveys, analysis of data and modelling efforts. The watershed characteristics are derived using geographical information system, whereas the morphometry of the lakes is investigated by undertaking bathymetry surveys. The hydrometeorological components of this lake system also were investigated through the development of relevant database and information systems, by identifying regional relationships, and by a rainfall-run-off model. These information systems have subsequently been integrated to model the water balance of the two lakes, and simulating the in-lake water levels. Several scenarios reflecting the natural conditions, water consumptive development possibilities, and sedimentation impacts have been investigated in this study. Based on the model simulation results, and on the computation of the life expectancies of the two lakes, it was found that sediment inflow and deposition significantly threaten their existence. [source] Evapotranspiration covers: An innovative approach to remediate and close contaminated sitesREMEDIATION, Issue 1 2003Kelly L. Madalinski A new, cost-effective option for the remediation and final closure of contaminated landfill sites gaining interest among environmental professionals is the evapotranspiration (ET) cover. Unlike current covers that use hydraulic barriers to prevent water from reaching the waste, ET covers rely on the simple concept of using water balance components to meet this goal. Depending on site conditions and other factors, ET covers may be less costly to construct, while still offering performance equivalent to conventional covers. While ET covers are being proposed, tested, or installed at a number of contaminated sites, field performance data remain limited. To address the need for more information, the U.S. Environmental Protection Agency (EPA) has been conducting several efforts to make available more information about this promising alternative solution. This article summarizes these efforts and provides information on the current status of using ET covers at contaminated sites. © 2003 Wiley Periodicals, Inc. [source] | ||||||||||