The Impact of Dynamic Environmental Flow Releases on Hydropower Production in the Zambezi River Basin

Incorporation of environmental flow releases from reservoirs has proven to be challenging due to fear of losses to existing water uses. Moreover environmental flow requirements (EFR) have not often been operationalized. This study compares the possibility of implementing dynamic EFR based on natural flows lagged against an upstream unregulated gauging point with static EFR. It simulates different scenarios with a high flow release in the wet season and analyses its impacts on hydropower production. This method accounts fully for the natural variability of environmental flows, implying less pressure on existing water uses during relatively dry years. Joint operation of two cascading dams vs. individual operation for EFR was also explored. These approaches were tested for the Zambezi River basin in Southern Africa using a water resources model, WAFLEX. Historic data on reservoir water levels, releases and power generation of the hydropower schemes were synthesized. Combining these yielded a validated series of monthly flow data for a 28 year period (1982‐2010). The results show that Kariba and Cahora Bassa reservoirs face a reduction in power produced when they would annually release an environmental flow. However, the dynamic EFR method entails smaller hydropower losses. Joint environmental flow operations will reduce overall basin power production more than if Cahora Bassa alone would release an environmental flow. However, such joint operation would be more beneficial to the ecosystem.     

去学水电站生态流量泄放措施优化研究

水电站的建设会造成坝址下游河段减水,对水环境和水生生物造成不利影响,因此电站生态流量的确定和泄放措施的可行性对于维护河流生态环境至关重要。以硕曲河去学水电站为例,基于可行性研究阶段提出的生态流量泄放措施方案,采用数学模型和理论分析方法,从生态流量取水水温、泄洪洞事故条件下生态流量保证率以及水资源的合理高效利用等方面进一步对生态流量泄放方案进行了优化比选。提出的优化方案提高了生态流量取水口的布置高程,在泄洪洞之外单独布置生态泄放系统,并增设生态流量发电机组等。对比分析表明,该优化方案在改善生态流量的下泄水温、提高生态流量泄放保证率、合理高效利用水能资源等方面具有较大优势。本研究为水电工程中生态流量泄放措施保障等方面提供了科学依据和技术参考。     

MULTIOBJECTIVE REAL‐TIME RESERVOIR OPERATION WITH A NETWORK FLOW ALGORITHM1

ABSTRACT: A network flow algorithm has been developed for the optimization of real‐time operation of a multiple reservoir system. Two purposes have been considered in the operation: flood control and hydropower generation. A special network structure was developed which allows the consideration of river routing. A multiobjective formulation is utilized thus allowing generation of a non‐dominated curve. The effect of imperfect forecast on the performance of the real‐time operation model is also evaluated. An application is made to a subsystem of the Brazilian hydroelectric system, located in the Paranapanema river basin. In this case study, the model showed good performance under the largest flood of the historical records.     

MULTIOBJECTWE OPTIMIZATION OF RESERVOIR SYSTEMS OPERATION1

ABSTRACT: Development of optimal operational policies for large-scale reservoir systems is often complicated by a multiplicity of conflicting project uses and purposes. A wide range of multiobjective optimization methods are available for appraising tradeoffs between conificting objectives. The purpose of this study is to provide guidance as to those methods which are best suited to dealing with the challenging large-scale, nonlinear, dynamic, and stochastic characteristics of multireservoir system operations. As a case study, the selected methodologies are applied to the Han River Reservoir System in Korea for four principal project objectives: water supply and low flow augmentation; annual hydropower production, reliable energy generation, and minimization of risk of violating firm water supply requirements. Additional objectives such as flood control are also considered, but are imposed as fixed constraints.     

Does collaboration affect the duration of environmental permitting processes?

While collaborative governance has many benefits for environmental planning and management, those benefits are not politically feasible if they impact on process efficiency. This study assesses collaboration's effect on the duration of water permitting processes, specifically the United States’ Federal Energy Regulatory Commission's hydropower relicensing process. Collaboration was measured using a survey of participants in 24 recent hydropower relicensing processes. A Cox proportional hazards model with mixed effects assessed the relationship between collaboration, regulatory framework, hydropower facility characteristics, and relicensing process duration. Collaboration was not associated with time to license. Instead, process duration depended on the regulatory framework (especially the switch to the Integrated Licensing Process and presence of endangered species) and facility characteristics (generating capacity and facility type). The results suggest that agencies should consider engaging collaboratively during planning and permitting, given that collaboration's benefits to decision quality do not incur a cost on overall process time.     

Analysis of Daily Peaking and Run‐of‐River Operations with Flow Variability Metrics,Considering Subdaily to Seasonal Time Scales

Environmental flows are an important consideration in licensing hydropower projects as operational flow releases can result in adverse conditions for downstream ecological communities. Flow variability assessments have typically focused on pre‐ and post‐dam conditions using metrics based on daily averaged flow values. This study used subdaily and daily flow data to assess environmental flow response to changes in hydropower operations from daily peaking to run‐of‐river. An analysis tool was developed to quantify flow variability metrics and was applied to four hydropower projects. Significant differences were observed between operations at the 99% confidence level in the median flow values using hourly averaged flow datasets. Median daily rise and fall rates decreased on average 34.5 and 27.9%, respectively, whereas median hourly rise and fall rates decreased on average 50.1 and 50.6%, respectively. Differences in operational flow regimes were more pronounced in the hourly averaged flow datasets and less pronounced or nonexistent in the daily averaged flow datasets. These outcomes have implications for the development of ecology‐flow relationships that quantify effects of flow on processes such as fish stranding and displacement, along with habitat stability. Results indicate that flow variability statistics should be quantified using subdaily datasets to accurately represent the nature of hydropower operations, especially for daily peaking facilities.     

Determination of optimum minimum flow from a dam by using energy analysis

The proposed restoration of an abandoned hydroelectric dam on the Quinebaug River, Connecticut, is studied using energy analysis. The analysis considers the effects of alternative minimum flow releases, ranging from 0 to 34 cubic meters per second (cms), on the total energy flow of the affected system. The principal system components affected by differing minimum flows are hydroelectric power generation, aquatic habitat, and gross aquatic ecosystem productivity.The minimum flow alternative resulting in the highest annual energy flow in the affected system is considered optimal. From this purely analytical point of view, the optimum minimum flow is 0 cms, due to the short length and low productivity of the regulated reach, and the lack of floodplain interactions.Simulations of longer and more productive river reaches were conducted. For very short, unproductive reaches, in the absence of a floodplain, the contribution of aquatic community productivity to total system energy flow is negligible compared to hydroelectric generation. Optimum minimum flows are higher for longer and more productive reaches. For such cases the operation of hydroelectric dams could reduce total system energy flow because the energy supplied by hydroelectric generation may be offset by losses in aquatic productivity due to diminished riverine habitat.     

Climate Change Impacts on Water Resources in the Upper Blue Nile River Basin,Ethiopia1

Kim, Ungtae and Jagath J. Kaluarachchi, 2009. Climate Change Impacts on Water Resources in the Upper Blue Nile River Basin, Ethiopia. Journal of the American Water Resources Association (JAWRA) 45(6):1361‐1378. Abstract: Climate change affects water resources availability of international river basins that are vulnerable to runoff variability of upstream countries especially with increasing water demands. The upper Blue Nile River Basin is a good example because its downstream countries, Sudan and Egypt, depend solely on Nile waters for their economic development. In this study, the impacts of climate change on both hydrology and water resources operations were analyzed using the outcomes of six different general circulation models (GCMs) for the 2050s. The outcomes of these six GCMs were weighted to provide average future changes. Hydrologic sensitivity, flow statistics, a drought index, and water resources assessment indices (reliability, resiliency, and vulnerability) were used as quantitative indicators. The changes in outflows from the two proposed dams (Karadobi and Border) to downstream countries were also assessed. Given the uncertainty of different GCMs, the simulation results of the weighted scenario suggested mild increases in hydrologic variables (precipitation, temperature, potential evapotranspiration, and runoff) across the study area. The weighted scenario also showed that low‐flow statistics and the reliability of streamflows are increased and severe drought events are decreased mainly due to increased precipitation. Joint dam operation performed better than single dam operation in terms of both hydropower generation and mean annual storage without affecting the runoff volume to downstream countries, but enhancing flow characteristics and the robustness of streamflows. This study provides useful information to decision makers for the planning and management of future water resources of the study area and downstream countries.     

乌江干流梯级电站生态调度现状分析

乌江是我国十三大水电基地之一,主要的开发任务为发电,其次为航运,兼顾防洪及其他。本研究在乌江干流上选取了4个具有代表性的断面,运用修正的Tennant法和综合法计算了维持乌江干流各代表性河段基本健康所需的生态需水量。研究表明,目前乌江干流梯级电站采取的调度措施能够满足各代表性河段所需的最小生态需水量。但目前的调度措施仍是建立在发电效益最大化基础上的,未能从干流生态环境系统的特殊要求进行调度,给干流生态环境造成了一定影响。本文最后提出了从多方面开展乌江干流梯级电站生态调度研究工作的建议。     

基于栖息地模拟的重口裂腹鱼繁殖期适宜生态流量分析

介绍了栖息地模拟方法原理及步骤,以姜射坝水电站减水段为例,应用栖息地模拟模型PHABSIM计算了重口裂腹鱼繁殖期适宜生境需水量。结果表明,该河段内重口裂腹鱼繁殖期适宜生态流量为40.6m3/s,其与水文学法的结果对比表明,该流量可以满足维持水生生物良好的生存条件的要求。指出当工程河段涉及珍稀鱼类关键生境时,采用栖息地模拟法确定受影响河段的生态需水量,可以更好地保护珍稀鱼类关键生境。研究结果可为已建电站减水河段生态修复工作提供依据,为拟建电站水生生态环境影响评价工作提供借鉴。     

Riparian vegetation instream flow requirements: A case study from a diverted stream in the Eastern Sierra Nevada,California, USA

A methodology is described that allows determination of instream flow requirements for maintenance of riparian trees. Tree-ring data revealed strong relationships between tree growth and stream flow volume for riparian species at Rush Creek, an alluvial stream within an arid setting; these relationships allowed development of models that predict growth rates from hydrologic variables. The models can be used to assess instream flow requirements under the assumption that certain levels of growth are necessary to maintain the population. There is a critical need for development and use of instream flow methodologies for riparian vegetation, since present methodologies focus on needs of aquatic animals (e.g., fish) and may underestimate needs of the entire riparian ecosystem.     

Ecotoxicological effects assessment in the Netherlands: Recent developments

In a recently published annex to the National Environmental Policy Plan of the Netherlands (1989), attention was paid to ecotoxicological effects assessment. The proposed procedure was based on the advice of the Health Council of the Netherlands (1989) on risk assessment of toxic chemicals for ecosystems. The various extrapolation methods described by the Health Council are critically discussed in this paper. The extrapolation method of Van Straalen and Denneman (1989) is evaluated for eight chemicals and 11 aquatic species. Conclusions are drawn about the quality and quantity of the ecotoxicological data needed for aquatic effects assessment. For the soil—a compartment that is often at risk—ecotoxicological effects assessment is not possible because suitable ecotoxicological test methods still have to be developed.     

Effectiveness of a publicly-funded demonstration program to promote management of dryland salinity

Community and catchment-based approaches to salinity management continue to attract interest in Australia. In one such approach, Catchment Demonstration Initiative (CDI) projects were established by the Western Australian (WA) Government in 2000 for targeted investment in large-scale catchment-based demonstrations of integrated salinity management practices. The aim was to promote a process for technically-informed salinity management by landholders. This paper offers an evaluation of the effectiveness of one CDI project in the central wheatbelt of WA, covering issues including: its role in fostering adoption of salinity management options, the role of research and the technical requirements for design and implementation of on-ground works, the role of monitoring and evaluation, the identification and measurement of public and private benefits, comparison and identification of the place and value of plant-based and engineering-based options, reliance on social processes and impacts of constraints on capacity, management of governance and administration requirements and an appreciation of the value of group-based approaches.A number of factors may reduce the effectiveness of CDI-type approaches in facilitating landholder action to address salinity, many of these are socially-based. Such approaches can create considerable demands on landholders, can be expensive (because of the planning and accountability required) on the basis of dollars per hectare impacted, and can be difficult to garner ownership from all involved. An additional problem could be that few community groups would have the capacity to run such programs and disseminate the new knowledge so that the CDI-type projects can impact outside the focus catchment. In common with many publicly-funded approaches to salinity, we found that direct benefits on public assets are smaller than planned and that results from science-based requirements of monitoring and evaluation have long lead times, causing farmers to either wait for the information or act sooner and take risks based on initial results. We also found that often it is a clear outline of the process that is of most importance in decision making as opposed to the actual results. We identified limitations in regulatory processes and the capacity for local government to engage in the CDI.The opportunities that CDI-type approaches provide centre around the value of its group-based approach. We conclude that they can overcome knowledge constraints in managing salinity by fostering group-based learning, offer a structured process of trialling options so that the costs and benefits can be clearly and transparently quantified, and avoid the costly mistakes and “learning failures” of the past.     

Making a stronger case for industrial energy efficiency by quantifying non-energy benefits

This paper describes a more compelling case for industry to promote the non-energy benefits of energy efficiency investments. We do this in two ways to actively appeal to chief executive officers (CEOs) and chief financial officers (CFOs) primary responsibility: to enhance shareholder value. First, we describe the use of a project-by-project corporate financial analysis approach to quantify a broader range of productivity benefits that stem from investments in energy-efficient technologies, including waste reduction and pollution prevention. Second, and perhaps just as important, we present such information in corporate financial terms. These standard, widely-accepted analysis procedures are more credible to industry than the economic modeling done in the past because they are structured in the same way corporate financial analysts perform discounted cashflow investment analyses on individual projects. Case studies including such financial analyses, which quantify both energy and non-energy benefits from investments in energy-efficient technologies, are presented. Experience shows that energy efficiency projects’ non-energy benefits often exceed the value of energy savings, so energy savings should be viewed more correctly as part of the total benefits, rather than the focus of the results. Quantifying the total benefits of energy efficiency projects helps companies understand the financial opportunities of investments in energy-efficient technologies. Making a case for investing in energy-efficient technologies based on energy savings alone has not always proven successful. Evidence suggests, however, that industrial decision makers will understand energy efficiency investments as part of a broader set of parameters that affect company productivity and profitability.     

MEETING THE CHALLENGE OF POLICY-RELEVANT SCIENCE: LESSONS FROM A WATER RESOURCE PROJECT1

ABSTRACT: Water resource scientists face complex tasks in evaluating aspects of water projects, but relatively few assessment procedures have been applied and accepted as standard applications. Decision-makers often rely on environmental assessments to evaluate the value and operation of projects. There is often confusion about scientists' role in policy decisions. The scientist can affect policy-making as an expert withess, an advocate or a surrogate. By understanding the policy process, scientists can make their work more “policy relevant.” Using the Terror Lake hydro project in Alaska as a guide, three lessons are discussed: (1) not all problems are able to be solved with technology; (2) policy-relevant technology is rarely imposed on a problem; and (3) the scientist need not just react to the policy process, but can have an impact on how that process unfolds.     

Public Lakes, Private Lakeshore: Modeling Protection of Native Aquatic Plants

Protection of native aquatic plants is an important proenvironmental behavior, because plant loss coupled with nutrient loading can produce changes in lake ecosystems. Removal of aquatic plants by lakeshore property owners is a diffuse behavior that may lead to cumulative impacts on lake ecosystems. This class of behavior is challenging to manage because collective impacts are not obvious to the actors. This paper distinguishes positive and negative beliefs about aquatic plants, in models derived from norm activation theory (Schwartz, Adv Exp Soc Psychol 10:221–279, 1977) and the theory of reasoned action (Fishbein and Ajzen, Belief, attitude, intention, and behavior: an introduction to theory and research, Addison-Wesley, Boston 1975), to examine protection of native aquatic plants by Minnesota lakeshore property owners. We clarify how positive and negative evaluations of native aquatic plants affect protection or removal of these plants. Results are based on a mail survey (n = 3,115). Results suggest that positive evaluations of aquatic plants (i.e., as valuable to lake ecology) may not connect with the global attitudes and behavioral intentions that direct plant protection or removal. Lakeshore property owners’ behavior related to aquatic plants may be driven more by tangible personal benefits derived from accessible, carefully managed lakeshore than intentional action taken to sustain lake ecosystems. The limited connection of positive evaluations of aquatic plants to global attitudes and behavioral intentions may reflect either lack of knowledge of what actions are needed to protect lake health and/or unwillingness to lose perceived benefits derived from lakeshore property.     

OPTIMAL OPERATION OF SHELBYVILLE AND CARLYLE LAKES1

ABSTRACT: Dams were built by the U. S. Army Corps of Engineers on the Kaskaskia River at Shelbyville and Carlyle in Illinois, in 1969 and 1967, respectively. The operation of the Shelbyville and Carlyle Lakes has changed over the years because of considerably lower bankfull channel capacities downstream of the dams than were adopted in the project designs. This study was conducted to review the present operation policy. Intent was to derive a policy for maximizing the overall benefits (or minimizing the overall damages) and to compare these benefits or damages with those with the present policy. The operating rules were optimized through a simulation model which was structured considering the physical nature of the system and the desirable operation in the best interest of various beneficial uses. The expected annual value of overall benefits from recreation and agriculture is shown to increase by $0.2 million with the optimal policy. With the optimal operation, the overall damages are reduced by 76 percent on the average over the 24 years of flow record at Shelbyville and Carlyle.     

Environmental Effects of Aquifer Overexploitation: A Case Study in the Highlands of Mexico

There are several environmental processes occurring under aquifer overexploitation conditions. These processes include groundwater table decline, subsidence, attenuation and drying of springs, decrease of river flow, and increased pollution vulnerability, among others processes. Some of these effects have been observed on the Upper Basin of the Lerma River. The Lerma River begins in the SE of the Valley of Toluca at 2,600 m asl, in the wetland known as Lagoons of Almoloya del Río. This wetland is made up of a group of lagoons, which are an important aquatic system from an environmental point of view. The water inflow of this wetland is a discharge of springs, which occur between the fractured volcanic material of the mountain range and granular volcanic–continental deposits of the Valley of Toluca aquifer. The intensive exploitation of the Valley of Toluca aquifer to supply urban and industrial water to Mexico City and Toluca began in 1950 and is responsible for a steady decline of piezometric levels of 1–3.5 m/yr. Other effects of this exploitation—the drying of the wetland, the decrease of river flow and the land subsidence—caused serious ecological and social impacts. The authorities declared this aquifer as overexploited in order to reduce the exploitation and preserve the availability of water resources in this important region.     

LOW-HEAD HYDROPOWER IMPACTS ON STREAM DISSOLVED OXYGEN1

ABSTRACT: A method to evaluate the effect of hydropower development on downstream dissolved oxygen (DO) is presented for a low head dam. Water, previously aerated during release over spillways and under gates, is diverted through the hydropower facility without further aeration. The oxygen transfer that occurs as a result of air entrainment at the various release points of a dam is measured. Oxygen transfer efficiencies are calculated and incorporated into an oxygen transfer model to predict average release DO concentrations. This model is used to systematically determine the effect of hydropower operation on downstream DO. Operational alternatives are investigated and a simple operational guide is developed to mitigate the effects of hydropower operation. Combinations of reduced generation and optimal releases from the dam allow the hydropower facility to operate within DO standards.     

IMPACTS OF CLIMATE CHANGE ON AQUATIC ECOSYSTEM FUNCTIONING AND HEALTH1

ABSTRACT: We review published analyses of the effects of climate change on goods and services provided by freshwater ecosystems in the United States. Climate-induced changes must be assessed in the context of massive anthropogenic changes in water quantity and quality resulting from altered patterns of land use, water withdrawal, and species invasions; these may dwarf or exacerbate climate-induced changes. Water to meet instream needs is competing with other uses of water, and that competition is likely to be increased by climate change. We review recent predictions of the impacts of climate change on aquatic ecosystems in eight regions of North America. Impacts include warmer temperatures that alter lake mixing regimes and availability of fish habitat; changed magnitude and seasonality of runoff regimes that alter nutrient loading and limit habitat availability at low flow; and loss of prairie pothole wetlands that reduces waterfowl populations. Many of the predicted changes in aquatic ecosystems are a consequence of climatic effects on terrestrial ecosystems; shifts in riparian vegetation and hydrology are particularly critical. We review models that could be used to explore potential effects of climate change on freshwater ecosystems; these include models of instream flow, bioenergetics models, nutrient spiraling models, and models relating riverine food webs to hydrologic regime. We discuss potential ecological risks, benefits, and costs of climate change and identify information needs and model improvements that are required to improve our ability to predict and identify climate change impacts and to evaluate management options.