Climate change impact to dam Operation, case study of Darma Dam, West Java

Darma Dam is located in the upstream of Cisanggarung River, Kuningan Regency, West Java Province. Darma Dam construction dated from about 1922. Indonesian government continued the construction and began operating in 1962. With effective storage of about 40 million m3, Darma Dam provides water for about 22 thousand irrigation areas and bulk water for several cities and regencies. Several problems encountered in Darma Dam operation and water management are 1) increasing water demand from domestic and industrial sectors, and 2) high inflow variation during the dry and wet season, resulting in a large amount of water spill from the dam spillway. This paper addressed the impact of climate change on the inflow variation of Darma Dam in the dry and wet seasons. Further analysis shows average water spills from the spillway during the wet season may increase from about 12 million m3/year in the present condition to about 20 million m3/year in 2020-2050, while the average water volume during the dry season may reduce from 22.5 million m3 in the present condition to about 20.7 million m3 in 2020-2050. This study suggests that dam operation need adjustment in the future as part of adaptation to climate change.

Willingness to Pay for Public Benefit Functions of Daecheong Dam Operation: Moderating Effects of Climate Change Perceptions

This study estimates the economic value of the Daecheong Dam for the public function of responding to climate change. It examines the moderating effect of climate change perceptions on value estimates by applying choice experiments (CE). The study specifies three dam function attributes—drought management (DM), flood control (FC), and water quality monitoring (WM)—subdivided into three levels to improve the existing conditions. Survey data from 603 households living in Daejeon, Chungbuk, and Chungnam have been collected to perform the CE. Subsequently, two clusters—high-involvement and low-involvement groups—have been extracted, based on the climate change perception index. The main results of comparing the marginal willingness-to-pay between the two clusters are as follows. The attributes and price variable significantly affected the choice probability to benefit from improvements in the rational signs of the coefficients. This does not violate the independence of the irrelevant alternatives assumption. The improvement values of high-involvement and low-involvement groups are estimated as KRW 21,570 and KRW 14,572 a year per household, respectively. Both show the same value intensities in the order of WM, DM, and FC.

Toward hyper-resolution global hydrological models including human activities: application to Kyushu Island, Japan

Global hydrological models that include human activities are powerful tools for assessing water availability and use at global and continental scales. Such models are typically applied at a spatial resolution of 30 arcminutes (approximately 50 km). In recent years, some 5-arcminute (9-km) applications have been reported, but with numerous technical challenges, including the validation of calculations for more than a million grid cells and the conversion of simulation results into meaningful information relevant to water resource management. Here, the H08 global water resources model was applied in two ways to Kyushu Island in Japan at resolution of 1 arcminute (2 km), and the detailed results were compared. One method involved feeding interpolated global meteorological and geographic data into the default global model (GLB; in accordance with previous high-resolution applications). For the other method, locally derived boundary conditions were input to the localized model (LOC; this method can be easily extended and applied to other regions, at least across Japan). The results showed that GLB cannot easily reproduce the historical record, especially for variables related to human activities (e.g., dam operation and water withdrawal). LOC is capable of estimating natural and human water balance components at daily time scales and providing reliable information for regional water resource assessment. The results highlight the importance of improving data preparation and modeling methods to represent water management and use in hyper-resolution global hydrology simulations.

Collaborative management of the Grand Ethiopian Renaissance Dam increases economic benefits and resilience

The landscape of water infrastructure in the Nile Basin is changing with the construction of the Grand Ethiopian Renaissance Dam. Although this dam could improve electricity supply in Ethiopia and its neighbors, there is a lack of consensus between Ethiopia, Sudan, and Egypt on the dam operation. We introduce a new modeling framework that simulates the Nile River System and Egypt’s macroeconomy, with dynamic feedbacks between the river system and the macroeconomy. Because the two systems “coevolve” throughout multi-year simulations, we term this a “coevolutionary” modeling framework. The framework is used to demonstrate that a coordinated operating strategy could allow the Grand Ethiopian Renaissance Dam to help meet water demands in Egypt during periods of water scarcity and increase hydropower generation and storage in Ethiopia during high flows. Here we show the hydrological and macroeconomic performance of this coordinated strategy compared to a strategy that resembles a recent draft proposal for the operation of the dam discussed in Washington DC.

Effects of Hydropower Dam Operation on Riverbank Stability

The increasing number of extreme climate events has impacted the operation of reservoirs, resulting in drastic changes in flow releases from reservoirs. Consequently, downstream riverbanks have experienced more rapid and frequent changes of the river water surface elevation (WSE). These changes in the WSE affect pore water pressures in riverbanks, directly influencing slope stability. This study presents an analysis of seepage and slope stability for riverbanks under the influence of steady-state, drawdown, and peaking operations of the Roanoke Rapids Hydropower dam on the lower Roanoke River, North Carolina, USA. Although the riverbanks were found to be stable under all the discharge conditions considered, which indicates that normal operations of the reservoir have no adverse effects on riverbank stability, the factor of safety decreases as the WSE decreases. When the role of fluvial erosion is considered, riverbank stability is found to reduce. Drawdown and fluctuation also decrease the safety factor, though the rate of the decrease depends more on the hydraulic conductivity of the soils rather than the discharge pattern.

Fish farmers’ perceived environmental effects on dam operation and coping strategies used in Ikere George Dam of Iseyin, Oyo State

The study examined the fish farmers‟ perceived environmental effects of dam operation and coping strategies among fish farmers in Ikere George dam, Iseyin Oyo state. Multi stage sampling technique was used to select 102 respondents in the study area. Data were collected through the use of interview schedule and were analysed using descriptive statistics such as percentage and frequency, while chi-square and PPMC were used to analyse hypotheses at p < 0.05. The result revealed that majority (54%) of the respondents below 40 years, with males predominantly higher than females. Also, 71.6% were married and 58.8% had educational attainment below secondary school. Challenges identified were disruption of movement of aquatic animals (137), blockage of migrations of aquatic species (135) and problem of overcrowding in the community (129) were prominent perceived effects of dam operation. The result further showed that migration (99) and planting of trees (146) were the most commonly used coping strategies. Chi-square showed that there was significant relationship between socio-economic characteristics of the respondents and perceived effects of dam operation except religion which was not significant (p>0.05). PPMC analysis revealed that there was significant relationship between coping strategies used (r=0.687, p=0.000). It is therefore recommended that proper training and adequate facilities should be given to fish farmers to ensure sustainability of the dam.

Unaccounted CO2 leaks downstream of a large tropical hydroelectric reservoir

Recent studies show that tropical hydroelectric reservoirs may be responsible for substantial greenhouse gas emissions to the atmosphere, yet emissions from the surface of released water downstream of the dam are poorly characterized if not neglected entirely from most assessments. We found that carbon dioxide (CO2) emission downstream of Kariba Dam (southern Africa) varied widely over different timescales and that accounting for downstream emissions and their fluctuations is critically important to the reservoir carbon budget. Seasonal variation was driven by reservoir stratification and the accumulation of CO2 in hypolimnetic waters, while subdaily variation was driven by hydropeaking events caused by dam operation in response to daily electricity demand. This “carbopeaking” resulted in hourly variations of CO2 emission up to 200% during stratification. Failing to account for seasonal or subdaily variations in downstream carbon emissions could lead to errors of up to 90% when estimating the reservoir’s annual emissions. These results demonstrate the critical need to include both limnological seasonality and dam operation at subdaily time steps in the assessment of carbon budgeting of reservoirs and carbon cycling along the aquatic continuum.

Monitoring Inflow Dynamics in a Multipurpose Dam Based on Travel-Time Principle

Understanding inflow dynamics in a dam lake forms the basis for optimal dam operation and management practices. However, methods pertaining to adequately determining negative inflows and addressing them, as well as quantifying uncertainties in dam inflow, have been scarcely investigated. In this study, the inflow was observed using two pairs of fluvial acoustic tomography (FAT) systems placed diagonally in a dam lake, forming a crossed-shaped pattern. The “travel-time” principle is the primary approach for measuring the inflow by FAT. The novelty of this study is in discussing the inflow characteristics within a slow water-flow environment monitored by FAT. Based on the reciprocal sound transmission, we upgraded an equation to estimate the flow direction; this newly proposed generalized equation can be used in a fluctuating flow environment. We also discussed the sound propagation characteristics for slow flow velocities. Finally, we demonstrated that a small inaccuracy in the acoustic signal, even by a sub-millisecond, can cause significant errors in measurements. One of the novel findings of this study is the detection of internal waves using the improved flow direction equation and acoustic travel-time records. Overall, this study presents a promising approach for inflow measurements under extremely slow flow conditions.

Prioritization of hydroelectric power plant earth dam safety procedures: a multicriteria approach

The number of procedures focused on dam safety is very large, mainly due to the rules established by different regulatory bodies, the guidelines that are part of the recommended best practices for engineering works, and the common sense and conservatism present in dam operation and maintenance because of the large socioeconomic and environmental impacts that any incident with a dam can cause. In practice, the vulnerability of a dam is inversely proportional to the improvement of safety procedures, such as monitoring and sensing, and the staff's capacity to interpret the information in timely fashion. Therefore, establishing priorities for these procedures is essential for the plant management to define the scheduling and detailing of inspections and monitoring, as well as training needs. The MCDA model described here was specified based on regulations and practical public domain guidelines. The subjective estimation of preferences was done by the staff of a hydroelectric plant located in central Brazil. It employed the Simos method combined with a procedure adopted to convert the scores to the format of paired comparisons. The weights for dam safety procedures were obtained using the fuzzy AHP method. The method allowed obtaining the classification of safety procedures according to their priorities, and thus provided the plant management with elements to better schedule monitoring and staff training.