Water, Volume 6, Issue 10 (October 2014) – 19 articles , Pages 2849-3246

Domestic rainwater harvesting (DRWH) is widely recognized as an alternative source of water in Taiwan because of water shortages. This suggests that rainwater potential should be maximized and quantified. In this article, we assess the potential of DRWH at a national level. To consider the climatic, building characteristic, economic, and ecological aspects of DRWH, we propose three categories: (1) theoretical; (2) available; and (3) environmental bearable rainwater potential. Four main steps were followed to develop the proposed framework: (1) Fifteen rainfall zones across Taiwan were generated through cluster analysis based on the average annual 10-day rainfall distributions of rainfall stations and administrative districts; (2) The roof area in each rainfall zone was estimated using a geographic information system (GIS) and land use classification database; (3) The weighted percentage of rainwater use in each rainfall zone was determined by the optimal point on the storage capacity and rainwater supply reliability curve for an equivalent building from each building type; (4) The percentage of the total roof area used to harvest rainwater in each region depends on the downstream impact of the stream flow. The procedures developed in this study constitute an effective tool for preliminarily estimation of the national DRWH potential. Full article

Since the first impoundment of Three Gorges Dam in 2003, algal blooms occur frequently in the near-dam tributaries. It is widely recognized that the impoundment-induced change in hydrodynamic condition with the lower current velocity will make the eutrophication problem even more severe when an excessive amount of nutrients is already loaded into a reservoir and/or its tributaries. Operation tests carried out by Three Gorges Corporation in 2010 point to some feasible reservoir operation schemes that may have positive impacts on reducing the algal bloom level. In our study, an attempt is made to obtain, through a numerical hydrodynamic and water quality modeling and analysis, the reservoir operation rules that would reduce the level of algal blooms in the Xiangxi River (XXR), a near-dam tributary. Water movements and algal blooms in XXR are simulated and analyzed under different scenarios of one-day water discharge fluctuation or two-week water level variation. The model results demonstrate that the reservoir operations can further increase the water exchange between the mainstream of the Three Gorges Reservoir (TGR) and the XXR tributary and thus move a larger amount of algae into the deep water where it will die. Analysis of the model results indicate that the water discharge fluctuation constituted of a lower valley-load flow and a larger flow difference for the short-term operation (within a day), the rise in water level for the medium-term operation (e.g., over weeks), and the combination of the above two for the long-term operation (e.g., over months) can be the feasible reservoir operation rules in the non-flood season for TGR. Full article

Low-lying coastal regions and their populations are at risk during storm surge events and high freshwater discharges from upriver. An integrated storm surge and flood inundation modeling system was used to simulate storm surge and inundation in the Tsengwen River basin and the adjacent coastal area in southern Taiwan. A three-dimensional hydrodynamic model with an unstructured grid was used, which was driven by the tidal elevation at the open boundaries and freshwater discharge at the upriver boundary. The model was validated against the observed water levels for three typhoon events. The simulation results for the model were in reasonable agreement with the observational data. The model was then applied to investigate the effects of a storm surge, freshwater discharge, and a storm surge combined with freshwater discharge during an extreme typhoon event. The super Typhoon Haiyan (2013) was artificially shifted to hit Taiwan: the modeling results showed that the inundation area and depth would cause severe overbank flow and coastal flooding for a 200 year return period flow. A high-resolution grid model is essential for the accurate simulation of storm surges and inundation. Full article

Scale-dependent parameter models were developed and nested to the Soil and Water Assessment Tool-SWAT to simulate climate and land use change impacts on water-sediment-nutrient yields in Benin at a regional scale (49,256 km²). Weighted contributions of relevant landscape attributes characterizing the spatial pattern of ongoing hydrological processes were used to constrain the model parameters to acceptable physical meanings. Climate change projections (describing a rainfall reduction of up to 25%) simulated throughout the Regional Model-REMO, very sensitive to a prescribed degradation of land cover, were considered. Land use change scenarios in which the population growth was translated into a specific demand for settlements and croplands (cropland increase of up to 40%) according to the development of the national framework, were also considered. The results were consistent with simulations performed at the meso-scale (586 km²) where local management operations were incorporated. Surface runoff, groundwater flow, sediment and organic N and P yields were affected by land use change (as major effects) of −8% to +50%, while water yield and evapotranspiration were dominantly affected by climate change of −31% to +2%. This tendency was more marked at the regional scale as response to higher scale-dependent rates of natural vegetations with higher conversions to croplands. Full article

The development of a decision support system (DSS) to inform policy making has been progressing rapidly. This paper presents a generic framework and the development steps of a decision tool prototype of geographic information systems (GIS)-based decision support system of river health diagnosis (RHD-DSS). This system integrates data, calculation models, and human knowledge of river health status assessment, causal factors diagnosis, and restoration decision making to assist decision makers during river restoration and management in Zhejiang Province, China. Our RHD-DSS is composed of four main elements: the graphical user interface (GUI), the database, the model base, and the knowledge base. It has five functional components: the input module, the database management, the diagnostic indicators management, the assessment and diagnosis, and the visual result module. The system design is illustrated with particular emphasis on the development of the database, model schemas, diagnosis and analytical processing techniques, and map management design. Finally, the application of the prototype RHD-DSS is presented and implemented for Xinjiangtang River of Haining County in Zhejiang Province, China. This case study is used to demonstrate the advantages gained by the application of this system. We conclude that there is great potential for using the RHD-DSS to systematically manage river basins in order to effectively mitigate environmental issues. The proposed approach will provide river managers and designers with improved insight into river degradation conditions, thereby strengthening the assessment process and the administration of human activities in river management. Full article

Climate change and its consequences present one of the most important threats to water resources systems which are vulnerable to such changes due to their limited adaptive capacity. Water resources in arid mountain regions, such as Al Jabal Al Akhdar; northern Sultanate of Oman, are vulnerable to the potential adverse impacts of environmental and climate change. Besides climatic change, current demographic trends, economic development and related land use changes are exerting pressures and have direct impacts on increasing demands for water resources and their vulnerability. In this study, vulnerability assessment was carried out using guidelines prepared by United Nations Environment Programme (UNEP) and Peking University to evaluate four components of the water resource system: water resources stress, water development pressure, ecological health, and management capacity. The calculated vulnerability index (VI) was high, indicating that the water resources are experiencing levels of stress. Ecosystem deterioration was the dominant parameter and management capacity was the dominant category driving the vulnerability on water resources. The vulnerability assessment will support policy and decision makers in evaluating options to modify existing policies. It will also help in developing long-term strategic plans for climate change mitigation and adaptation measures and implement effective policies for sustainable water resources management, and therefore the sustenance of human wellbeing in the region. Full article

Knowledge about water flow paths is essential for understanding biogeochemical fluxes in developed agricultural landscapes, i.e., the input of nutrients into surface waters, soil erosion, or pesticide fate. Several methods are available to study rainfall-runoff processes and flux partitioning: hydrometric based approaches, chemical tracers, modeling, and stable isotope applications. In this study a multi-method approach was conducted to gain insights into the hydrological fluxes and process understanding within the complex anthropogenic-influenced catchment of the Vollnkirchener Bach, Germany. Our results indicate that the catchment responds differently to precipitation input signals and dominant runoff-generation processes change throughout the year. Rainfall-induced runoff events during dry periods are characterized by a temporarily active combined sewer overflow. During stormflow, a large contribution of fast event water is observed. At low flow conditions losing and gaining conditions occur in parallel. However, when catchment’s moisture conditions are high, an ephemeral source from clay shale-graywacke dominated forested sites becomes active. The study reveals that the collection of detailed distributed hydrometric data combined with isotopic tracers, provides fundamental information on the complex catchment behavior, which can finally be utilized for conceptualizing water fluxes at a small catchment scale. Full article

Growing water scarcity, due to growing populations and varying natural conditions, puts pressure on irrigation systems, which often are the main consumptive water users. Therefore, water resources management to improve the allocation of limited water supplies is essential. In this study, a non-linear programming optimization model with an integrated soil/water balance is developed to determine the optimal reservoir release policies and the optimal cropping pattern around Doroudzan Dam in the South-West of Iran. The proposed model was solved using a genetic algorithm (GA). Four weather conditions were identified by combining the probability levels of rainfall, evapotranspiration and inflow. Moreover, two irrigation strategies, full irrigation and deficit irrigation were modeled under each weather condition. The results indicate that for all weather conditions the total farm income and the total cropped area under deficit irrigation were larger than those under full irrigation. In addition, our results show that when the weather conditions and the availability of water changes the optimal area under corn and sugar beet decreases sharply. In contrast, the change in area cropped with wheat is small. It is concluded that the optimization approach has been successfully applied to Doroudzan Dam region. Thus, decision makers and water authorities can use it as an effective tool for such large and complex irrigation planning problems. Full article

Assessment of the diverse responses of water resources to climate change and high concentrations of CO₂ is crucial for the appropriate management of natural ecosystems. Despite numerous studies on the impact of climate change on different regions, it is still necessary to evaluate the impact of these changes at the local scale. In this study, the Soil and Water Assessment Tool (SWAT) model was used to evaluate the potential impact of changes in temperature, rainfall and CO₂ concentration on water resources in a rural catchment in NW Spain for the periods 2031–2060 and 2069–2098, using 1981–2010 as a reference period. For the simulations we used compiled regional climate models of the ENSEMBLES project for future climate input data and two CO₂ concentration scenarios (550 and 660 ppm). The results showed that changes in the concentration of CO₂ and climate had a significant effect on water resources. Overall, the results suggest a decrease in streamflow of 16% for the period 2031–2060 (intermediate future) and 35% by the end of the 21st century as a consequence of decreasing rainfall (2031–2060: −6%; 2069–2098: −15%) and increasing temperature (2031–2060: 1.1 °C; 2069–2098: 2.2 °C). Full article

This study quantifies the sensitivity of surface runoff to drought and climate change in the Diyala watershed shared between Iraq and Iran. This was achieved through a combined use of a wide range of changes in the amount of precipitation (a decline between 0% and −40%) and in the potential evapotranspiration rate (an increase between 0% and +30%). The Medbasin-monthly rainfall-runoff model (Medbasin-M) was used for runoff simulation. The model was calibrated for twelve hydrologic years (1962−1973), and the simulation results were validated with the observed annual runoff for nine water years (1974−1982). For the calibration period, the correlation coefficient (r), the root mean squared error (RMSE), the mean absolute error (MAE) and the index of agreement (IoA) were 0.893, 2.117, 1.733 and 0.852, respectively. The corresponding values for validation were 0.762, 1.250, 1.093 and 0.863, in this order. The Reconnaissance Drought Index (RDI) and the Streamflow Drought Index (SDI) were analysed using DrinC software. Three nomographs were introduced to quantify the projected reductions in the annual runoff and the anticipated RDI and SDI values, respectively. The proposed methodology offers a simple, powerful and generic approach for predicting the rate of change (%) in annual runoff under climate change scenarios. Full article

Runoff and sediment loads have exhibited significant changes over the past six decades in the Yellow River Basin, China. The current study evaluates the changing trends and regime shifts in runoff and sediment loads at both the annual and monthly time scales. The associated spatial and temporal variations are analyzed by a sequential t-test analysis of the regime shifts (STARS) approach and the “breaks for additive seasonal and trend” (BFAST) model using hydrological data at eight stations from the 1950s to 2011. Both runoff and sediment loads exhibit significant declines (p < 0.05), except in the upper reaches of the river near the Tangnaihai station. The regime shifts detected by the STARS approach are not completely consistent with the results from the BFAST method. In most cases, the regime shifts occurred in 1969 and 1986, due to the construction of large reservoirs. Climate change and other human activities, such as large-scale soil and water conservation measures, can result in abrupt changes in hydrological series at some stations. The trapping effects of reservoirs not only cause regime shifts of runoff and sediment loads, but also adjust their inter-annual and seasonal distributions. Various soil and water conservation measures are responsible for the significant reduction in runoff and sediment loads in the mid-lower reaches of the Yellow River Basin. In addition, water withdrawals from both river runoff and ground water play a critical role in the changing trends in runoff and indirectly alter the sediment loads. The findings provide a good reference for the effective promotion of climate change adaptation, water resources planning and river basin management. Full article

In the current study, the applicability of the Annandale method was verified based on the results of silting and sediment distribution measurements carried out in eight small reservoirs, with a capacity that does not exceed 5 million m³. It was found that the application of this method is possible only in the case of small reservoirs, in which the sediment load is deposited in the near-dam zone. The results of studies conducted on small reservoirs allowed the construction of a graph presenting the relationship of a sum of dimensionless sediment load volume as a function of relative distance from the dam, which became the modification of the graph in Annandale’s method. The proposed modification of Annandale’s method considers reservoirs with a length less than 1000 m and capacity-inflow ratio ranging from a few per mille to a percent. Full article

The effective management of high ammonium containing wastewater is important for the sustainable development of the wastewater industry. A pre-denitrification and post-nitrification two-sludge system was proposed to treat high ammonium containing wastewater with low carbon-to-nitrogen (C/N) ratios. In the system, pre-denitrification was adopted to use organic carbon in raw wastewater efficiently for nitrogen removal, while post-nitrification was adopted to achieve nitritation. System performance and the characteristics of nitrous oxide (N₂O) emission were examined. As to the influent chemical oxygen demand (COD) and ammonium nitrogen (NH₄-N) concentration, both 800 mg/L, nitrogen removal was mainly through pre-denitrification, and the nitrogen removal percentage was 43.4%. In post-nitrification, nitritation was achieved with a nitrite accumulation efficiency of 97.8% and a NH₄-N removal loading rate of 0.45 g/(L·d). With nitrite as the electron acceptor during denitrification, its removal rate increased, while the N₂O emission factor decreased with increasing C/N ratios. Nitrification was affected significantly by the aeration rate. When the aeration rate was below 0.6 L/min, the NH₄-N removal rate increased, while the N₂O emission rate decreased with increasing aeration rates. However, when the aeration rate was above 0.6 L/min, it had little influence on N₂O emission. During nitrification, N₂O emission factors decreased exponentially with increasing ammonium oxidation rates. Full article

This paper provides an overview of the special issue on “Water policy, productivity and economic efficiency”. In particular, it includes an overview of key topics on the future of water as a productive factor, in the context of alternative uses and perspective scenarios. The selected papers cover a wide range of relevant economic issues and are presented in three categories: productivity assessment, institutional framework and mechanisms, and governance aspects. The paper concludes by discussing future research challenges in this field. Full article

The integrity of the Blesbok Spruit catchment has been significantly compromised over the past decades, mainly due to the discharge of mining effluent and sewage. This research investigated the hydrological responses, in terms of water quality, in the event of land cover change within the catchment to make predictions on the future sustainability of the region’s water resources with the application of Partial Least Squares (PLS) regression analysis. The quantification of hydrological responses in terms of water quality towards land cover changes has not been completed by previous research studies within the catchment. This research established the catchment’s present state of water quality and formulated PLS model equations to enable the prediction of future concentrations of specific water quality parameters in association with future land cover change. A change in land cover was found to have various negative influences. The retransformation of land cover into natural areas is accompanied with unintended and undesirable effects due to the degradation of the catchment’s buffering capabilities and the absence of the enforcement of the decommissioning of mining operations. For the Blesbok Spruit catchment to avoid a future water predicament, systematic and interdisciplinary measures need to be implemented according to these and other related findings, to ensure the future sustainability of the catchment and the region as a whole. Full article

The aim of this study was to estimate the determinants of residential water demand for chief towns of every Italian province, in the period 2007–2009, using the linear mixed-effects model estimated with the restricted-maximum-likelihood method. Results confirmed that the applied tariff had a negative effect on residential water consumption and that it was a relevant driver of domestic water consumption. Moreover, income per capita had a positive effect on water consumption. Among measured climatic and geographical features, precipitation and altitude exerted a strongly significant negative effect on water consumption, while temperature did not influence water demand. Further, data show that small towns in terms of population served were characterized by lower levels of consumption. Water utilities ownership itself did not have a significant effect on water consumption but tariffs were significantly lower and residential water consumption was higher in towns where the water service was managed by publicly owned water utilities. However, further research is needed to gain a better understanding of the connection between ownership of water utilities and water prices and water consumption. Full article

This article is a study of water scarcity in Cyprus, examining the implications on the demand and supply side of water under the transformations caused by economic development, urbanisation and environmental changes. Measures and actions taken by water stakeholders to tackle the water poverty issue are discussed and assessed, together with possible future solution methods. In the light of the success of global climate models to forecast future conditions and advances in integrated management tools, the suggestion here is the need for a global systems approach to help guide policy decisions. Full article

Over the past several decades, dissolved organic carbon (DOC) in inland natural water systems has been a popular research topic to a variety of scientific disciplines. Part of the attention has been due to observed changes in DOC concentrations in many of the water systems of the Northern Hemisphere. Shifts in DOC levels, and changes in its composition, are of concern due to its significance in aquatic ecosystem functioning and its potential and realized negative effects on waters that might be treated for drinking purposes. While it may not be possible to establish sound cause and effect relationships using a limited number of drivers, through long-term DOC monitoring studies and a variety of laboratory/field experiments, several explanations for increasing DOC trends have been proposed, including two key mechanisms: decreased atmospheric acid deposition and the increasing impact of climate change agents. The purpose of this review is three-fold: to outline frequently discussed conceptual mechanisms used to explain DOC increases (especially under a changing climate), to discuss the structure of DOC and the impact of higher levels of DOC on drinking water resources, and to provide renewed/sustained interest in DOC research that can encourage interdisciplinary collaboration. Understanding the cycling of carbon from terrestrial ecosystems into natural waters is necessary in the face of a variable and changing climate, as climate change-related mechanisms may become increasingly responsible for variations in the inputs of allochthonous DOC concentrations in water. Full article

In this study, the stable isotope values of oxygen and hydrogen were used to identify the seasonal contribution ratios of precipitation to groundwater recharge in the Hualien River basin of eastern Taiwan. The differences and correlations of isotopes in various water bodies were examined to evaluate the groundwater recharge sources for the Hualian River basin and the interrelations between groundwater and surface water. Proportions of recharge sources were calculated based on the results of the mass balance analysis of the isotope composition of hydrogen and oxygen in the basin. Mountain river water accounted for 83% and plain rainfall accounted for 17% of the groundwater recharge in the Huanlian River basin. Using the mean d-values, a comparison of d-values of precipitation and groundwater indicates the groundwater consists of 75.5% wet seasonal sources and 24.5% dry seasonal sources, representing a distinct seasonal variation of groundwater recharge in the study area. Comparisons between hydrogen and oxygen isotopes in rainwater showed that differences in the amount of rainfall resulted in depleted oxygen and hydrogen isotopes for precipitation in wet seasons as compared to dry seasons. The river water contained more depleted hydrogen and oxygen isotopes than was the case for precipitation, implying that the river water mainly came from the upstream catchment. In addition, the hydrogen and oxygen isotopes in the groundwater slightly deviated from the hydrogen and oxygen isotopic meteoric water line in Huanlian. Therefore, the groundwater in this basin might be a mixture of river water and precipitation, resulting in the effect of the river water recharge being greater than that of rainfall infiltration. Full article