Target Water Levels Research Articles

Variable target water level control method in front of sluice in flood storage area based on storage balance model

Abstract To prevent the increase in flood disaster frequency, scale, and impact degree, a flood control engineering system with flood storage and detention areas, embankments, and reservoirs as the main body has been formed. Flood storage area is the key to the flood control engineering system, and its water level control performance is directly related to the success of flood control. According to the actual situation, the flood evolution simulation model in the flood storage area is constructed to obtain the evolution information of any unit of flood in the flood storage area. The dynamic control judgment coefficient of the water level is calculated, and the dynamic control program of the variable target water level in front of the sluice is formulated. Water level control can be realized by executing the established procedures. The above experimental data show that the proposed method can effectively control the water level in the flood storage area within the range of 26.03m ∼ 29.12m, and the minimum value of the corresponding risk rate is 3%, which fully proves that the proposed method has better dynamic control effect on the variable target water level in front of the sluice.

A Study on the Rainfall-Storage Volume-Target Water Level Curve for Flood Control on the Small Size Dam: Case study for Goesan Dam

Dams in South Korea serve various functions, including water supply, hydropower, and transportation; in particular, they are responsible for a significant portion of flood control. This study aims to propose a methodology that field engineers can easily utilize to assess the hydrological conditions of small dams that require simultaneous discharge during flood inflow due to limited storage capacity. Therefore, the relationship between rainfall, storage volume, and target water level was established for dams. This relationship is represented as a curve and is based on the storage volume during the rising phases of floods. Historical data of the Goesan Dam, located in the Dalcheon Basin of the Han River, including inflow, discharge, and rainfall were collected at 10-minute intervals. Analysis was conducted on four major flood events occurring since 2018. The proposed methodology was applied to derive the rainfall-storage volume-target water level curve for the Goesan Dam. Subsequently, the appropriate flood response water level for the Gosan Dam was calculated, and its applicability was examined.

High greenhouse gas emissions after grassland renewal on bog peat soil

Drained agriculturally used peatlands are hotspots for greenhouse gas (GHG) emissions, especially carbon dioxide (CO2) and nitrous oxide (N2O). To reduce GHG emissions and simultaneously maintain intensive grassland use, raising water levels by subsurface irrigation (SI) is controversially discussed. Both, intensive grassland use and installations of SI may require grassland renewal. We investigated an experimental intervention site (INT) (SI target water levels: -0.30 m) and a deeply drained reference site (REF), both intensive grassland on deep bog peat. After installation of the SI system, a mechanical grassland renewal took place at INT. At both sites, CO2 (eddy covariance), N2O and methane (manual closed chamber technique) were measured. Additionally, soil water was analyzed for nitrogen species. Here, we report on the initial year of GHG measurements including grassland renewal and rising water levels. Overall, GHG emissions were strongly influenced by grassland renewal at INT. Despite progressively rising water levels, soil moisture in the upper centimeters was low and thus grass growth was slow, resulting in an almost complete loss of harvest. This resulted in a net ecosystem carbon balance (NECB) of 4.64 ± 1.03 t C ha−1 containing only 0.57 ± 0.09 t C ha−1 harvest at INT, while NECB at REF was 6.08 ± 1.74 t C ha−1 including harvest from five grass cuts. Methane fluxes were negligible at both sites. Nitrous oxide emissions dominated the GHG balance at INT. With 144.5 ± 45.5 kg N2O–N ha–1 a–1, they were much higher than at REF (3.9 ± 3.1 kg N2O–N ha–1 a–1) and any other values published so far. Peak fluxes occurred when nitrate concentrations in soil water were extremely high, soil moisture was increased, and vegetation development was struggling. This study highlights the risk of grassland renewals on peat soils regarding yield losses as well as high GHG emissions.

Itô-theory-based multi-time scale dispatch approach for cascade hydropower-photovoltaic complementary system

The complementary operation of cascade hydropower (CHP) and photovoltaic (PV) can increase the integration of PV power and has become a trend in modern power systems. However, the randomness and variability of PV power output might cause challenges in precisely tracking the submitted generation plan of the CHP-PV complementary system. The safety and stability of the receiving-end power grid might deteriorate. In this paper, a multi-time scale dispatch framework with day-ahead and intra-day dispatch is established for the CHP-PV complementary system to address the PV uncertainties. The day-ahead dispatch is employed to provide reliable reference results and sufficient adjustment reservations for the intra-day dispatch. An Itô-theory-based stochastic optimization (ITB-SO) approach is proposed for the intra-day dispatch by modeling the PV prediction error with stochastic differential equations (SDE). The SDE model can be embedded into the ITB-SO approach without scenario generation, and thus computational burden can be significantly reduced compared with scenario-based methods. A complementary system in southwest China is chosen as a detailed case study. The simulation results demonstrate that real-time random PV fluctuations could be compensated by adjusting CHPs. Meanwhile, the target water level of cascade reservoirs can be tracked under the proposed approach.

Development of an Integrated Water Resource Scheduling Model Based on Platform Plug-In: A Case Study of the Wudu Diversion and Irrigation Area, China

Integrated water resource scheduling is a key strategy for controlling river floods as well as for promoting the benefits and abolishing the harmful aspects of water conservancy projects. It is necessary to explore an effective development mode to address the current issues of long development times and poor outcomes for integrated water resource scheduling models. Drawing on the concept of software reuse, a development mode for an integrated water resource scheduling model is offered based on “platform system + model plug-in”, the cores of which are plug-in modules and interface integration. The boundaries and connection relations of each plug-in module are formed based on the logical analysis of the model plug-in. A web application mode is used to implement a standardized interface, which can be quickly and seamlessly connected to the system platform. The model is explored and applied in the Wudu diversion and irrigation area in China. The generated model is eventually verified using data obtained from two flood periods. According to the simulation results, the gate operation will be convenient, and the target water level will be attained in the allocated time with a satisfactory peak-clipping effect. It shows both good coordination and great utilization value of the plug-in modules. The concept of designing a plug-in database is eventually taken into consideration for combining and generating an optimization model of each river.

Development of Simple Method for Flood Control Capacity Estimation of Dam in South Korea

As flood damage is becoming more frequent and severe worldwide, efficient flood control of dams has been highlighted. The purpose of the study is to establish a simple method for dam operators to estimate the flood control capacity and predischarge level required for flood response. The cumulative probability distribution (CDF) pair with the same return period for 12 major dams located in South Korea were estimated using the frequency matching method. A Ratio of Storage volume to Flood inflow (RSF) concept was suggested and applied for each dam, and they were classified into three types: Linear, Estranged, and Vague according to the water storage characteristics. Using the method presented in this study, we suggested the required amount of flood control capacity and target water level for each dam. The results demonstrated that there is no linear relationship between flood and storage of dam when the ratio of watershed area to a storage capacity of the dam is 2.0 or more, or the ratio of watershed area to flood control capacity is 20.0 or more. Further, it was found that the RSF value is affected by the initial water level of the dam when a high flood inflow was observed for Estranged and Vague types. It is expected that the method presented in this study can be basic information for performing predischarge for flood control in numerous dams.

Influence of Subsurface Pipe Perforations on Transient Water Table Response and Steady Soil-Water Flux under Subirrigation

HighlightsWater table rise was slower under a sparsely perforated pipe as compared to a pipe that was densely perforated.Response time increased as buried pipe depth decreased for both combinations of perforation characteristics.Fluxes from buried pipes spaced at 15 m in loamy sand satisfied the water demand for cereal/grain crops (6 mm d-1).Increasing perforation density on the pipe wall is the most effective way to reduce exit head losses.Abstract. It is important to consider the water table rise into the unsaturated zone when designing subsurface irrigation systems that consist of buried perforated corrugated pipes. Corrections to pipe spacing equations for head losses due to perforations are based on the entrance resistance, which is derived for buried pipes operating in drainage mode. However, the boundary condition at the soil-pipe interface when operated in subsurface irrigation mode requires the use of the exit resistance to accurately account for perforations in the pipe wall. Simulations of a subsurface irrigation system with four soil textures, three lateral pipe spacings, and three buried depths were carried out, with the numerical model COMSOL, to demonstrate the effects of variable perforation characteristics on the transient water table rise into the unsaturated zone. Soil-water fluxes were also computed for the system when operated under steady-state conditions. The simulated water table rise exceeded or approached a predetermined target water level of 1.65 m above the buried pipes in coarse-textured soils (loamy sands and silt loams) with lateral pipe spacings as large as 10 m. Increasing the number and length of rectangular slots in the pipe wall (densely perforated) can reduce the water table response time to reach the target level by 15 h in a silt loam soil and 25 h in a clay soil. The optimum pipe spacing needed to sustain a soil-water flux of 6 mm d-1 (common to eastern Canada and the U.S. Midwest) can be increased from 15.1 to 16.2 m in loamy sands by using densely perforated pipes. In contrast, increasing perforations in pipes buried in clays and sandy clays will result in pipe spacing increases of less than 0.2 m because these fine-textured soils have lower hydraulic conductivity. This study has demonstrated that variable perforation characteristics can be included in the analysis and design of subsurface drainage systems for improving water management. Keywords: Corrugated perforated pipes, Exit resistance, Head loss, Subirrigation, Unsaturated zone, Water table response.

농업용 저수지의 홍수기 제한수위 설정 및 수문운영기준 개발

In this study, a method to secure flood control capacity using emergency gates of agricultural reservoirs, which generally do nat have flood control, was studies. In the case of the Sungju reservoir the target water level of this study, a plan to maintain the limited water level during the flood season was reviewed by pre-releasing 70%, 65% and 60% of the effective storage capacity. By changing the opening of the emergency gate from the initial water level condition, a pre-release condition that can satisfy the limited water level during the flood period is suggested. In addition, the water level after 24-hours of pre-release was set as the initial water level at the time of flood inflow, and the 24 hours rainfall was analyzed for 200mm to 600 mm. It was analyzed that damage could be reduced. Lastly, the conditions of emergency gate opning according to water level conditions is presented for the operation of the flood season through the pre-release of the Sungju reservoir, so that it can be used as a reference for the operation of the flood season of the Sungju reservoir.

A study for the target water level of the dam for flood control

A study for the target water level of the dam for flood control

Hydrogeochemical modeling for groundwater management in arid and semiarid regions using MODFLOW and MT3DMS: A case study of the Jeffara of Medenine coastal aquifer, South‐Eastern Tunisia

AbstractThe study of water quality and the quantification of reserves and their variations according to natural and anthropogenic forcing is necessary to establish an adequate management plan for groundwater resources. For this purpose, a modeling approach is a useful tool that allows, after calibration phase and verification of simulation, and under different scenarios of forcing and operational changes, to estimate and control the groundwater quantity and quality. The main objective of this study is to collect all available data in a model that simulates the Jeffara of Medenine coastal aquifer system functioning. To achieve this goal, a conceptual model was constructed based on previous studies and hydrogeological investigations. The regional groundwater numerical flow model for the Jeffara aquifer was developed using MODFLOW working under steady‐state and transient conditions. Groundwater elevations measured from the piezometric wells distributed throughout the study area in 1973 were selected as the target water levels for steady state (head) model calibration. A transient simulation was undertaken for the 42 years from 1973 to 2015. The historical transient model calibration was satisfactory, consistent with the continuous piezometric decline in response to the increase in groundwater abstraction. The developed numerical model was used to study the system's behavior over the next 35 years under various constraints. Two scenarios for potential groundwater extraction for the period 2015–2050 are presented. The predictive simulations show the effect of the increase of the exploitation on the piezometric levels. To study the phenomenon of salinization, which is one of the most severe and widespread groundwater contamination problems, especially in coastal regions, a solute transport model has been constructed by using MT3DMS software coupled with the groundwater flow model. The best calibration results are obtained when the connection with the overlying superficial aquifer is considered suggesting that groundwater contamination originates from this aquifer.Recommendations for water resource managers The results of this study show that Groundwater resources of Jeffara of Medenine coastal aquifer in Tunisia are under immense pressure from multiple stresses. The water resources manager must consider the impact of economic and demographic development in groundwater management to avoid the intrusion of saline water. The results obtained presented some reference information that can serve as a basis for water resources planning. The model runs to provide information that managers can use to regulate and adequately control the Jeffara of Medenine water resources.

Integrating wind, photovoltaic, and large hydropower during the reservoir refilling period

Hydropower facilities are an ideal solution to complement the intermittent production of energy from wind and solar photovoltaic facilities in electric power systems. However, adding this task to the multiple diverse duties of a reservoir (e.g., flood mitigation, water supply, and power generation) poses a challenge related to pursuing multiple and sometimes conflicting objectives. This study proposes an approach for integrating hydro, wind, and photovoltaic power during a reservoir’s refill period. Specifically, this approach simultaneously minimizes the fluctuation in the combined power output of these three resources and maximizes their combined power generation while adhering to the target reservoir’s water levels. The proposed approach uses a multiobjective optimization model that prescribes a day-ahead optimal hourly operation for a hydropower facility in terms of spilled water, water stored in the reservoir, and water used for power generation, while meeting a daily target to refill the reservoir. The prescribed scheduling is then used as the input into a model that simulates the actual operations of the power system. This study focuses on a hydro-wind-photovoltaic system located in southwestern China, where the peak power generating capacity of the hydropower facility is ten percent larger than the combined installed capacity of the wind and solar power. The results show that by using the proposed model, the hydropower facility effectively smooths the fluctuations in the combined power output caused by variable wind and photovoltaic power and concurrently meets the reservoir replenishing targets under dry, moderate, or wet hydrologic scenarios. Furthermore, the trade-offs between power generation maximization and power fluctuation reduction were found to depend on two conditions: whether the reservoir is full, and whether the turbine is generating electricity at its maximum capacity. The hydro-wind-photovoltaic integration is more cost-effective when the reservoir is not full and the turbines are not generating electricity at their maximum capacity. When the reservoir is full, hydropower still has the ability to balance the wind and photovoltaic power without curtailment but tends to result in water spillage (22–402 m3/s) and reductions in electricity generation (0.1–11.4 GWh per day). The proposed method for scheduling operations allows hydropower facilities to complement wind and photovoltaic power output, while meeting the target water levels during the refill period.

Loon Nest Viability Model: A Performance Indicator for Improving Water-Level Regulation of Large Water Bodies

Rule curves dictating target water levels for management have been implemented in several water bodies in North America over the last 70 years or more. Anthropogenic alterations of water levels are known to affect several components of wetland ecosystems. Evaluating the influence of rule curves on biological components with simple performance indicators could help harmonize water level management with wetland integrity. We assessed the potential of using the probability of common loon nest viability as a performance indicator of long-term impacts of rule curves on nesting wetland birds. We analyzed the outcome of rule curves on the probability of loon nest viability in Rainy Lake and Namakan Reservoir, 2 regulated water bodies located along the Ontario-Minnesota border. The analysis was focused on 4 hydrological time series between 1950 and 2013: 2 sets of time series simulating rule curves used to manage the water bodies in the past decades (referred to as the 1970RC and 2000RC), one of the historical measured water levels, and one of computed natural water levels. The probability of loon nest viability under the 1970RC was 2× higher than under natural conditions in both water bodies. The probability was also 2× higher under the 2000RC than under the 1970RC in the Namakan Reservoir but not in Rainy Lake. The rule curves generally improved conditions for nesting loons in both water bodies. The presented performance indicator can be used to evaluate future rule curves before they are implemented in the Rainy-Namakan or other similar systems.

Complex relationship between seasonal streamflow forecast skill and value in reservoir operations

Abstract. Considerable research effort has recently been directed at improving and operationalising ensemble seasonal streamflow forecasts. Whilst this creates new opportunities for improving the performance of water resources systems, there may also be associated risks. Here, we explore these potential risks by examining the sensitivity of forecast value (improvement in system performance brought about by adopting forecasts) to changes in the forecast skill for a range of hypothetical reservoir designs with contrasting operating objectives. Forecast-informed operations are simulated using rolling horizon, adaptive control and then benchmarked against optimised control rules to assess performance improvements. Results show that there exists a strong relationship between forecast skill and value for systems operated to maintain a target water level. But this relationship breaks down when the reservoir is operated to satisfy a target demand for water; good forecast accuracy does not necessarily translate into performance improvement. We show that the primary cause of this behaviour is the buffering role played by storage in water supply reservoirs, which renders the forecast superfluous for long periods of the operation. System performance depends primarily on forecast accuracy when critical decisions are made – namely during severe drought. As it is not possible to know in advance if a forecast will perform well at such moments, we advocate measuring the consistency of forecast performance, through bootstrap resampling, to indicate potential usefulness in storage operations. Our results highlight the need for sensitivity assessment in value-of-forecast studies involving reservoirs with supply objectives.

A PSO approach for optimum design of dynamic inversion controller in water distribution systems

Water distribution systems have become immensely complex due to ever increasing water demand and sporadic availability of water at the sources. Generally, water management issues are handled through human intervention, which naturally leads to incompetent trial and error procedures. Moreover, the non-linear system dynamics and sequential pumping operations involved in the water distribution systems make the manual control tricky. Past studies suggest that system efficiencies can be tremendously enhanced by automatic control of such systems. However, the use of control algorithms is not yet in vogue among water engineers. Thus, to demonstrate the efficacy of auto-operated water distribution network, a water supply system dataset available in the literature has been considered as a case study in the present research. This study attempts to evaluate the performance of particle swarm optimization and Ziegler–Nichols tuned dynamic inversion control of pumps in maintaining the target water levels in a series of reservoirs, wherein the controller proficiency has been gauged for different initial conditions and non-constant demand inputs. The results indicate good performance and convergence characteristics of both the controllers and thus they can be used for real time operations.

Optimal design and dynamic control of construction dewatering with the consideration of dewatering process

Design optimization of construction dewatering has important values in protecting the surrounding environment and reducing the engineering cost. The existing dewatering design methods are mostly based on the optimization of pumping rate needed to maintain a stable water level, while the drop and rise of water level are not considered in the estimation of pumping rate and dewatering time. The dynamics process of construction dewatering is taken into account in this article. The method for calculating the total water yield and dewatering time from the initial groundwater level to the target water level is established. Then, the design optimization of well group dewatering is provided with the consideration of total water yield and dewatering time in dynamic dewatering process. Finally, the method for the calculation of total water yield and dewatering time when dewatering regions change is derived. The proposed method can realize design optimization and dynamic control of dewatering as the dewatering regions and water level changes in construction. The reliability of this method is verified in on-site engineering applications.

Influence of impounding process on the variation of phytoplankton and microcystin-LR in a tributary of Three Gorges Reservoir, China

Three Gorges Reservoir (TGR) was filled to the target water level for the first time in 2010 since the building of Three-Gorges Dam. The present study was carried out to investigate the influence of water storage process on phytoplankton density and microcystin-LR (MC-LR) concentration in Xiangxi Bay (XXB), a tributary of TGR. The results showed that the phytoplankton cell density varied from 51.5 × 105. L−1 to 121.25 × 105. L−1 and the mean value increased from the estuary to the upper part of XXB. The variation of phytoplankton cell density coincided with the variation of MC-LR equivalent concentrations which reach the highest concentration of 1.09 ± 0.35 µg. L−1 in impounding season. The study has provided an ideal model to investigate the MC-LR and relevant alga seasonal variation in a specific water body. Based on these findings, intensive attention should be paid to the water quality in the tributaries of TGR.

Evaluating changes to reservoir rule curves using historical water-level data

Flood control reservoirs are typically managed through rule curves (i.e. target water levels) which control the storage and release timing of flood waters. Changes to rule curves are often contemplated and requested by various user groups and management agencies with no information available about the actual flood risk of such requests. Methods of estimating flood risk in reservoirs are not easily available to those unfamiliar with hydrological models that track water movement through a river basin. We developed a quantile regression model that uses readily available daily water-level data to estimate risk of spilling. Our model provided a relatively simple process for estimating the maximum applicable water level under a specific flood risk for any day of the year. This water level represents an upper-limit umbrella under which water levels can be operated in a variety of ways. Our model allows the visualization of water-level management under a user-specified flood risk and provides a framework for incorporating the effect of a changing environment on water-level management in reservoirs, but is not designed to replace existing hydrological models. The model can improve communication and collaboration among agencies responsible for managing natural resources dependent on reservoir water levels.

Managing groundwater levels in the face of uncertainty and change: a case study from Gnangara

The Gnangara Groundwater System meets about 50% of all water needs for the Perth–Peel region of Western Australia (population 1.7 million). Much of the water is contained in an unconfined aquifer which occurs in coastal sand dunes and supports ecologically-important throughflow wetlands. The system has been subject to significant climate change since about 1975, although the persistent and unidirectional nature of the change was not recognised for some time. As well as climate, groundwater levels are affected by land use (e.g. plantation forestry, urbanisation) and land management (e.g. how plantations and stormwater are managed) as well as by the amount of groundwater abstraction from each of several inter-connected aquifers. Land, water and forests are managed by different government agencies with their own policy objectives. Maintaining groundwater levels within an agreed range of values to protect the wetlands requires informed and early adaptation by these agencies as well as a supportive community. Adaptation was hampered because there was little or no experience of managing groundwater for climate change and the causes of declining levels were neither clear nor agreed. Even when target water level decisions were agreed, their achievement required the cooperation of parties with different priorities. This paper examines some of the lessons learned from this experience and the current approach to manage the land, water and forest resources to meet multiple objectives in a system that is undergoing transitional change rather than reaching a new equilibrium. Climate change impacts have been progressive and the concept of a system that can respond in a resilient manner after a temporary perturbation is not an appropriate concept in this example. Climate adaptation involves significant social and institutional change as well as biophysical changes to make the most of a changing system.

EVALUATION OF DESIGN WATER LEVELS AT THE EMS-DOLLARD ESTUARY CONSIDERING THE EFFECT OF A STORM SURGE BARRIER

In the Ems-Dollard estuary at the southern North Sea coast a revaluation of design water levels along the German dykes has become necessary, since the safety margin for sea level rise was increased by 25 cm due to a decision of the Lower Saxon Ministry for Environment and Climate Protection. The upstream part of the estuary is protected against high storm surges by a storm surge barrier. The closure of the barrier effects downstream surge water levels due to partial reflection. Deterministic-mathematical modeling is applied to evaluate design water levels and design wave run-up. Three severe storm surge events have been hindcasted by a cascade of three hierarchical models from the Continental Shelf over the German Bight into the area of interest. The models are forced by non-stationary and spatially varying data of atmospheric pressure, wind velocities and directions available of meteorological model investigations. The verification of the storm surge model with water level observations yields good agreements. With respect to legal boundary conditions, the single-value-method is applied to determine the highest expected high water level at Emden. Starting from this target water level, the wind velocities in the meteorological boundary conditions are increased with the aim to increase the surge level at the coast and to match the predetermined design water level at Emden. The responding water levels in the Ems-Dollard estuary assign the new design water levels.

Information theory–based approach for location of monitoring water level gauges in polders

Data collection is a critical activity in the management of water systems because it supports informed decision making. Data are collected by means of monitoring networks in which water level gauges are of particular interest because of their implications for flood management. This paper introduces a number of modifications to previously published methods that use information theory to design hydrological monitoring networks in order to make the methods applicable to the design of water level monitors for highly controlled polder systems. The new contributions include the use of a hydrodynamic model for entropy analysis, the introduction of the quantization concept to filter out noisy time series, and the use of total correlation to evaluate the performance of three different pairwise dependence criteria. The resulting approach, water level monitoring design in polders (WMP), is applied to a polder in the Pijnacker region, Netherlands. Results show that relatively few monitors are adequate to collect the information of a polder area in spite of its large number of target water levels. It is found, in addition, that the directional information transfer DITYX is more effective in finding independent monitors, whereas DITXY is better for locating sets of monitors with high joint information content. WMP proves to be a suitable and simple method as part of the design of monitoring networks for polder systems.