Evaluation of the Impact of Best Management Practices on Streamflow,Sediment and Nutrient Yield at Field and Watershed Scales

Water Resources Management - Evaluating Best Management Practices (BMPs) in watersheds using hydrologic and water quality models can help to establish an effective watershed water management. Soil...     

Best Management Practices Optimization at Watershed Scale: Incorporating Spatial Topology among Fields

Best management practices (BMPs) are widely used to reduce nonpoint source pollutions. In order to obtain cost-effective BMPs configurations, optimization methods are introduced. Recent studies show that knowledge on BMP placement can be used to improve existing algorithms for BMPs optimization. However, some important knowledge has not been fully utilized yet, one of which is about the spatial topology among fields and BMPs interactions. In this paper, a new method for BMPs optimization was proposed, which incorporated knowledge of BMPs interactions into a multi-objective genetic algorithm (i.e., ε-NSGAII) based on spatial topology among fields. Then this method was applied to the BMPs optimization in a small agricultural watershed in Southern Manitoba of Canada, and the performance was compared with those of conventional method. In order to make a comprehensive comparison, experiments were conducted under different population sizes (i.e., 60, 100, and 200) and different numbers of fields (i.e., 29, 52, and 79). The results showed that the proposed method was superior to conventional method on the aspect of greater sediment reductions (2% - 17%) at the same cost, and the Pareto curves obtained by the proposed method were more complete. This study demonstrated that incorporating spatial topology among fields into BMPs optimization can lead to better results and this finding could provide valuable references to similar studies.     

未来气候情景下覆被变化对径流量的影响

以陆浑水库控制流域为研究对象,利用流域DEM、土地利用数据、1987—2001年气候和水文观测数据,在率定SWAT模型参数的基础上,以SCS模型参数的变化来反映覆被变化,分析了未来气候变化情景及覆被变化情景对径流的影响。结果表明:2011—2050年在流域落叶林地面积退化30%情况下径流量将增大7.02%,落叶林地面积增加20%情况下径流量将减少8.48%。     

Combined Management of Groundwater Resources and Water Supply Systems at Basin Scale Under Climate Change

Water stress conditions associated with population growth, climate change, and groundwater contamination, represent a significant challenge for all stakeholders in the water sector. Increasing the resilience of Water Supply Systems (WSSs) becomes of fundamental importance: along with an adequate level of service, sustainability targets must be ensured. A long-term management strategy is strictly connected to a holistic approach, based on analyses at different scales. To this end, both groundwater modeling tools and water management models, with different spatial and temporal scales, are routinely and independently employed. Here, we propose a coupled approach combining: i) groundwater models (MODFLOW) to investigate different stress scenarios, involving climate change and anthropic activities; ii) water management models (Aquator), to assess the water resources availability and the best long-term management strategy for large-scale WSS. The management models are implemented starting from input and output flows derived by groundwater models: this leads to establish a comprehensive framework usually not defined in management models and including a quantitative characterization of the aquifer. The proposed methodology, general and applicable to any study area, is here implemented to the WSS of Reggio Emilia Province, and its main groundwater resource, the Enza aquifer, considering three different stress scenarios for groundwater models (BAU, ST1, and ST2), and for management strategies (BAU, BAU_RV2, ST2). Among the key results, we observe that coupling the two model types: i) allows evaluating water resources availability in connection with management rules; ii) leads to examining more realistic operation choices; iii) permits planning of infrastructures at basin scale.

     

Annual and Seasonal Variations of Hydrological Processes Under Climate Change Scenarios in Two Sub-Catchments of a Complex Watershed

The Elbow River watershed, located in the rain shadow of the Rocky Mountains in western Canada, is characterized by a complex hydrological regime due to significant differences in climate and geomorphological settings between the west and east sub-catchments. This watershed has experienced several extreme droughts and floods in the recent decades, which might be accentuated with climate change. This study was undertaken to investigate the average annual and seasonal variations of surface and sub-surface hydrological processes in the west and east sub-catchments along with and the entire watershed under five plausible GCM-scenarios up to 2070 using the physically-based, distributed MIKE SHE/MIKE 11 model. Most of the scenarios indicate a reduction in the average annual overland flow, groundwater recharge and baseflow in the east sub-catchment. The pattern of seasonal change generally exhibits a rise in overland flow, baseflow, evapotranspiration, groundwater recharge, and streamflow in winter-spring and a decline in summer-fall. The induced changes in hydrological processes are proportionally more perceptible in the east sub-catchment compared to the west sub-catchment. However, the west sub-catchment governs the watershed behaviour and determines the future changes, over-riding the stronger climate change signal in the east. This investigation indicates that a greater understanding of climate change impacts on the water balance of a watershed with significant differences in sub-regional settings is achieved when capturing the surface and subsurface hydrological process responses of each sub-catchment individually along with the entire watershed. Such information can guide water resources management by providing a more rigorous assessment of the processes involved in the watershed.     

Application of Artificial Neural Networks to Project Reference Evapotranspiration Under Climate Change Scenarios

Water Resources Management - Evapotranspiration is sensitive to climate change. The main objective of this study was to examine the response of reference evapotranspiration (ET0) under various...     

Evaluation of Water Resources Management Strategies to Overturn Climate Change Impacts on Lake Karla Watershed

The effects of climate change on meteorology, hydrology and ecology have become a priority area for research and for water management. It is crucial to identify, simulate, evaluate and, finally, adopt water resources management strategies to overturn the impacts of climate change. This paper is dealing with the assessment of climate change impacts on the availability of water resources and the water demands and the evaluation of water resources management strategies in the Lake Karla watershed, central Greece and it is a contribution to the “HYDROMENTOR” research project. The outputs of the Canadian Centre for Climate Modelling Analysis Global Circulation Model CGCM3 were downscaled using a statistical hybrid method to estimate monthly precipitation and temperature time series for present and future climate periods. The analysis was conducted for two future periods 2030–2050 and 2080–2100 and three SRES scenarios (A2, A1B and B1). The surface water and groundwater have been simulated for present and future climate periods using a modelling system, which includes coupled hydrologic models. Two operational strategies of hydro-technical project development are coupled with three water demand strategies. Overall, eight water management strategies are evaluated for present climate conditions and twenty four water management strategies for future climate conditions have been evaluated. The results show that, under the existing water resources management, the water deficit of Lake Karla watershed is large and it is expected to become critical in the future, even though the impact of climate change on the meteorological parameters is very moderate.     

Optimal Ecological Management Practices (EMPs) for Minimizing the Impact of Climate Change and Watershed Degradation Due to Urbanization

Massive deforestation induced by unplanned urbanization in the hilly watersheds of Brahmaputra basin, India, has led to ecological imbalance and is gradually transforming this basin into a multi-hazard zone. Removal of green cover is also becoming a matter of global concern, as it can accelerate the adverse impacts of climate change. People coming in search of work generally reside in the hills, as they cannot afford the high cost of land in plains. This has led to deforestation of the hilly area and has resulted in increased surface erosion from the upper catchments. Though sediment and water yield from these degraded watersheds could have been minimized by implementing ecologically sustainable management practices (EMPs), such as grass land, forest land and detention pond, poor economic conditions of the people stands in the way of field implementation. On the other hand, major industries, which can be held responsible for emission of greenhouse gases, can be asked to finance greenery development in these hilly watersheds through implementation of selected EMPs to earn carbon credit for them. To convert this concept into reality, the EMP combination must be selected in such a way that it restricts sediment and water yield from the watershed within the permissible limit and maximizes its carbon sequestration capacity at minimum possible cost. Such optimal planning is a prerequisite for preparing an acceptable logical agreement between Government and private companies. Keeping this in mind, an optimization model was developed and applied to a micro watershed of Guwahati to explore its applicability in actual field. The model developed in this study provides most logical carbon credit negotiation, subject to the availability of reliable value of CO₂ sequestration for different EMPs.     

气候变化情景下黄河天然径流预测研究

1961—2000年黄河天然径流量呈减小趋势,且径流变化与降水量变化过程基本一致。选用IPCC提出的A2、B2两种温室气体排放方案,并采用北京大学在黄河流域未来气候情景研究中的降尺度成果,以黄河流域未来气候情景模式和预测成果为基础,建立黄河水量平衡模型,预测黄河主要断面的未来天然径流量并分析其时空变化。结果表明:黄河径流量2050年将减少29.3亿～61.1亿m3,2100年将减少42.2亿～71.2亿m3;从空间分布来看,上游兰州以上主要产水区的降水量、径流量有较大幅度减小,其他区域产流量有所增加;从径流年内分配来看,冬季、春季略有增加或基本不变,夏季、秋季减少明显。     

Scenario Assessment of Streamflow Simulation and its Transition Probability in Future Periods Under Climate Change

The effect of climate change on water resources is an important challenge. To analyze the negative effects of this phenomenon and recommend adaptive measures, it is necessary to assess streamflow simulation scenarios and streamflow transition probabilities in future periods. This paper employs the HadCM3 (Hadley Centre Coupled Model, version 3) model to generate climate change scenarios in future periods (2010–2039, 2040–2069, and 2070–2099) and under A2 emission scenarios. By introducing climatic variable time series in future periods to the IHACRES (Identification of unit Hydrographs And Component flows from Rainfall, Evaporation and Streamflow data) hydrological model, long-term streamflow simulation scenarios are produced. By fitting statistically different distributions on runoff produced by using goodness-of-fit tests, the most appropriate statistical distribution for each month is chosen and relevant statistical parameters are extracted and compared with statistical parameters of runoff in the base period. Results show that long-term annual runoff average in the three future periods compared to the period 2000–1971 will decrease 22, 11, and 65 %, respectively. ?Despite the reduction in total runoff volume in future periods compared to the baseline period, the decrease is related to medium and high flows. In low flows, total runoff volumes for future periods compared to the baseline period will increase 47, 41, and 14 %, respectively. To further assess the impact of annual average runoff on flows, it is necessary to examine the correlation of time series using streamflow transition probabilities. To compare the streamflow transition probability in each of the future periods with base period streamflow in each month, streamflow is discretized and performance criteria are used. Results show a low coefficient of correlation and high error indicators.     

Streamflow Response to Climate Change in the Brahmani River Basin,India

Climate change can significantly affect the water resources availability by resulting changes in hydrological cycle. Hydrologic models are usually used to predict the impacts of landuse and climate changes and to evaluate the management strategies. In this study, impacts of climate change on streamflow of the Brahmani River basin were assessed using Precipitation Runoff Modeling System (PRMS) run under the platform of Modular Modeling System (MMS). The plausible hypothetical scenarios of rainfall and temperature changes were used to assess the sensitivity of streamflow to changed climatic condition. The PRMS model was calibrated and validated for the study area. Model performance was evaluated by using joint plots of daily and monthly observed and simulated runoff hydrographs and different statistical indicators. Daily observed and simulated hydrographs showed a reasonable agreement for calibration as well as validation periods. The modeling efficiency (E) varied in the range of 0.69 to 0.93 and 0.85 to 0.95 for the calibration and validation periods, respectively. Simulation studies with temperature rise of 2 and 4°C indicated 6 and 11% decrease in annual streamflow, respectively. However, there is about 62% increase in annual streamflow under the combined effect of 4°C temperature rise and 30% rainfall increase (T4P30). The results of the scenario analysis showed that the basin is more sensitive to changes in rainfall as compared to changes in temperature.     

The Economic Value of Groundwater Irrigation for Food Security Under Climate Change: Implication of Representative Concentration Pathway Climate Scenarios

Sustainable management of groundwater resources to support food security under the potential effects of climate change is an emerging area of research and particularly relevant in the context of Small Island Developing States. Employing three regional downscaled Representative Connection Pathway (RCP 2.6, RCP4.5, and RCP 8.5) emission scenarios that have been linked to an economic evaluation framework, the potential impact of climate change on groundwater scarcity, economic value of groundwater irrigation, food security, and farming livelihoods is investigated. A nonlinear hydro-economic framework, which integrates groundwater hydrology, climate data, land use, economics and institutions, has been applied for the island of Barbados. Results indicate that climate change would intensify the dependency on groundwater irrigation overtime, modulated by climate intensity. The strength of climate change will boost the marginal value of groundwater irrigation, as food price will scale up, presenting negative impacts on food security and reducing farming livelihoods. The climate change would also result in higher cost of producing foods resulting from increased cost of pumping, mainly driven by the effect of meeting abstraction needs for domestic and municipal consumption. Our primary results show that for a small island, sustaining groundwater resources will be a challenging objective to achieve under severe climate change.     

Economic Assessment of Best Management Practices in the Mara River Basin: Toward Implementing Payment for Watershed Services

The Mara River in East Africa is currently experiencing poor water quality and increased fluctuations in seasonal flow. Improved water quality will require upstream farmers and foresters to adopt Best Management Practices (BMPs), which might cost them considerably. This study proposes a Payment for Watershed Services (PWS) mechanism. This is a market-based approach, whereby downstream water users would pay upstream watershed service providers towards the costs of BMPs implementation. This study analyzes the technical feasibility and economic viability of adapting selected BMPs and provides cost estimates of a PWS program. Using three criteria of water quality improvement, economic feasibility, and technical suitability, a detailed economic opportunity cost analysis revealed that farmers would indeed incur economic losses for all BMPs except no-till farming. We also developed a multi-criteria (demographic and environmental) methodology for identifying land areas to be placed under BMPs. More than 122,000 ha of land would require BMPs, including a moratorium on agriculture inside the Mau Forest Complex. The initial per hectare opportunity costs across the five highest ranked BMPs ranged from US$ 272 to US$ 926. Using these cost estimates, the paper draws some valuable policy and management insights on how to finance BMP implementation.     

Scenarios for Restoring Floodplain Ecology Given Changes to River Flows Under Climate Change: Case from the San Joaquin River,California

Freshwater ecosystem health has been increasingly linked to floodplain connectivity, and some river restoration efforts now overtly target reconnecting floodplain habitats for species recovery. The dynamic nature of floodplain habitats is not typically accounted for in efforts to plan and evaluate potential floodplain reconnection projects. This study describes a novel approach for integrating streamflow dynamics with floodplain area to quantify species‐specific habitat availability using hydraulic modelling, spatial analysis and statistical measures of flow regime. We used this hydro‐ecological modelling approach to examine the potential habitat for splittail (Pogonichthys macrolepidotus), Chinook salmon (Oncorhynchus tshawytscha) and their food resources under two restoration treatments and two climate change flow scenarios for a study site on San Joaquin River in California. Even with the addition of new floodplain through restoration efforts, the modelling results reveal only 13 streamflow events in the past 80 years had the magnitude and duration required for splittail spawning and rearing, and 14 events had flows long enough for salmon rearing benefits. Under climate change, modelled results suggest only 4–17% of the years in the rest of this century are likely to produce required flow‐related habitat conditions for splittail and salmon rearing along the study reach. Lastly, we demonstrate by simulating augmented reservoir releases that restoration of fish habitat will require a more natural flow regime to make use of restored floodplain and achieve the desired hydrologic habitat connectivity. Copyright © 2014 John Wiley & Sons, Ltd.     

Identification of Streamflow Response to Climate Change and Human Activities in the Wei River Basin,China

In this study, the calibration and validation period with stable underlying surface conditions was determined by using a statistically significant change point of the annual streamflow in several catchments of the Wei River basin (WRB). The effects of climate changes and human activities on streamflow were estimated by using the sensitivity-based method and the dynamic water balance model, respectively. The contributions of climate effects and human activities effects on streamflow were also investigated. The results showed that almost all the catchments exhibited significant decreasing trend of streamflow in the early 1990s. The streamflow was more sensitive to changes in precipitation than changes in potential evapotranspiration (PET). Effects of climate due to changes in precipitation and PET are weak in Linjiacun, Weijiabao and Xianyang catchments, while it is strong in the catchments controlled by other hydrological stations, accounting for more than 40 % of streamflow reduction. Effects of human activities on streamflow in Linjiacun, Weijiabao, Xianyang and Zhangjiashan catchments accounted for more than 50 % of the streamflow reduction. The study provides scientific foundation to understand the causes of water resources scarcity and useful information for the planning and management of water resources in the ecological fragile arid area.     

Evaluation of Adaptation Scenarios for Climate Change Impacts on Agricultural Water Allocation Using Fuzzy MCDM Methods

Due to the impacts of climate change on agriculture and water allocation, an investigation of the farmers’ perceptions and stakeholders’ views on the adaptation strategies to climate change has a great of importance for sustainable development in the future. In this study, a fuzzy based decision support system has been developed to evaluate and rank the proposed adaptation scenarios to climate change in the Jarreh agricultural water resources system in southwest of Iran. Using output of ten coupled models inter comparison project phase 5 (CMIP5) under two representative concentration pathway scenarios (RCP 4.5, and RCP 8.5), the results indicated an increasing the annual mean temperature (1.64–1.84 °C under RCP 4.5, and 1.85–2.1 °C under RCP 8.5), reducing the amount of runoff into the reservoir (17.83–46.24% under RCP 4.5, and 21.54–50.91%under RCP 8.5), as well as increasing the amount of agricultural water requirement. Also, the results showed decreasing in reliability of system (12–53% under RCP 4.5, and 23–63% under RCP 8.5). Following, due to the main purpose of the system, six adaptation scenarios by using a questionnaire and stakeholders’ opinions are proposed to mitigate the effects of climate change. In the next step, by fuzzy mode of the technique for order of preference by similarity to ideal solution (TOPSIS) and fuzzy preference ranking organization method for enrichment of evaluations (PROMETHEE II), the proposed scenarios have been ranked according to the performance criteria. The final results of this study indicated the superiority of improving the irrigation efficiency and decreasing the area under cultivation among other proposed scenarios.

     

Sustainability of Small Reservoirs and Large Scale Water Availability Under Current Conditions and Climate Change

Semi-arid river basins often rely on reservoirs for water supply. Small reservoirs may impact on large-scale water availability both by enhancing availability in a distributed sense and by subtracting water for large downstream user communities, e.g. served by large reservoirs. Both of these impacts of small reservoirs are subject to climate change. Using a case-study on North-East Brazil, this paper shows that climate change impacts on water availability may be severe, and impacts on distributed water availability from small reservoirs may exceed impacts on centralised water availability from large reservoirs. Next, the paper shows that the effect of small reservoirs on water availability from large reservoirs may be significant, and increase both in relative and absolute sense under unfavourable climate change.     

Spatial Optimization of Best Management Practices to Attain Water Quality Targets

Diffuse nutrient loads are a common problem in developed and agricultural watersheds. While there has been substantial investment in best management practices (BMPs) to reduce diffuse pollution, there remains a need to better prioritize controls at the watershed scale as reflected in recent US-EPA guidance for watershed planning and Total Maximum Daily Load development. We implemented spatial optimization techniques among four diffuse source pathways in a mixed-use watershed in Northern Vermont to maximize total reduction of phosphorus loading to streams while minimizing associated costs. We found that within a capital cost range of 138 to 321 USD ha^-1 a phosphorus reduction of 0.29 to 0.38 kg ha^?1 year^?1, is attainable. Optimization results are substantially more cost-effective than most scenarios identified by stakeholders. The maximum diffuse phosphorus load reduction equates to 1.25 t year^?1using the most cost-effective technologies for each diffuse source at a cost of $3,464,260. However, 1.13 t year^?1 could be reduced at a much lower cost of $976,417. This is the practical upper limit of achievable diffuse phosphorus reduction, above which additional spending would not result in substantially more phosphorus reduction. Watershed managers could use solutions along the resulting Pareto optimal curve to select optimal combinations of BMPs based on a water quality target or available funds. The results demonstrate the power of using spatial optimization methods to arrive at a cost-effective selection of BMPs and their distribution across a landscape.     

Watershed Modeling to Assessing Impacts of Potential Climate Change on Water Supply Availability

Climate change could have impacts on hydrologic systems threatening, availability of water supply resources. In Illinois, regional water supply planning efforts are attempting to better understand potential impacts on low flow and surface water availability through analysis of hydrologic sensitivity to a range of climate scenarios. This paper explores the development, calibration and validation of Fox River watershed model using the soil and water assessment tool (SWAT) and the model’s application to assess impacts of potential climate change. The watershed model is calibrated and validated using daily flow records at three gauging stations. Automatic model calibration followed by manual refinement of parameter values was performed. Calibration results were generally good for monthly and annual time step but only satisfactory for daily simulations. Based on simulations of global climate models produced for IPCC fourth assessment report, climate scenarios were prepared by the Illinois State Water Survey for water supply planning initiatives in north-east and east-central Illinois. These scenarios showed ranges of temperature change between 0°C to +3.3°C and annual precipitation changes between −127 to +127 mm in the next 50 years, excluding the 5% extreme ends of those climate model simulations considered. Changes in climate were reflected using adjustments to the historical record, instead of using direct outputs from individual climate models. The watershed model was used to assess the impact of potential climate change. Application results indicate that annual precipitation change of 127 mm on average increases annual water yield and 7-day low flows by 28% and 19%, respectively. In contrast, a temperature change of +3.3°C results in average reductions of annual water yield by 13% and 7-day low flows by 10%. Seasonal effects were investigated through evaluation of changes in average monthly flows. Increasing precipitation resulted in significant changes in streamflows in late summer and fall months where as increasing temperature greatly affects winter flows due to snowmelt. The key implication is that climate change-induced variability of streamflows could have major impacts on water supply availability in the Fox River watershed and in particular, increased periods of drought could result in deficit of supplies during seasons of peak water use. It must be noted that this analysis does not examine the potential impacts of population growth and water use on water supply availability, which are also expected to have substantial influences in the region.     

Using Climate-Flood Links and CMIP5 Projections to Assess Flood Design Levels Under Climate Change Scenarios: A Case Study in Southern Brazil

The Intergovernmental Panel on Climate Change (IPCC) assessed with medium confidence that there has been an anthropogenic influence in the intensification of heavy rainfall at the global scale. Nevertheless, when taking into account gauge-based evidence, no clear climate-driven global change in the magnitude or frequency of floods has been identified in recent decades. This paper follows up on a previous nonstationary flood frequency analysis in the Itajaí River, which is located in the Southeastern South America region, where evidence of significant and complex relationships between El Niño-Southern Oscillation (ENSO) and hydrometeorological extremes has been found. The identified climate-flood link is further explored using sea surface temperature (SST) output from CMIP5 models under different representative concentration pathway (RCP) scenarios. Results are inconclusive as to whether it is possible to make a statement on scenario-forced climate change impacts on the flood regime of the Itajaí river basin. The overall outcome of the analysis is that, given that sample sizes are adequate, stationary models seem to be sufficiently robust for engineering design as they describe the variability of the hydrological processes over a large period, even if annual flood probabilities exhibit a strong year-to-year dependence on ENSO.