Quantifying Streamflow Depletion from Groundwater Pumping: A Practical Review of Past and Emerging Approaches for Water Management

Groundwater pumping can cause reductions in streamflow (‘streamflow depletion’) that must be quantified for conjunctive management of groundwater and surface water resources. However, streamflow depletion cannot be measured directly and is challenging to estimate because pumping impacts are masked by streamflow variability due to other factors. Here, we conduct a management-focused review of analytical, numerical, and statistical models for estimating streamflow depletion and highlight promising emerging approaches. Analytical models are easy to implement, but include many assumptions about the stream and aquifer. Numerical models are widely used for streamflow depletion assessment and can represent many processes affecting streamflow, but have high data, expertise, and computational needs. Statistical approaches are a historically underutilized tool due to difficulty in attributing causality, but emerging causal inference techniques merit future research and development. We propose that streamflow depletion-related management questions can be divided into three broad categories (attribution, impacts, and mitigation) that influence which methodology is most appropriate. We then develop decision criteria for method selection based on suitability for local conditions and the management goal, actionability with current or obtainable data and resources, transparency with respect to process and uncertainties, and reproducibility.

Groundwater lowering for construction of the Kilsby Tunnel – pumping and tunnelling

The Kilsby Tunnel, constructed in the 1830s under the direction of Robert Stephenson, faced severe problems when a section of the tunnel, almost 400 m long, was driven through water-bearing unstable ‘quicksand’ conditions. Contemporary methods were not well suited to tunnelling through such conditions, and in previous decades, several canal tunnels had been planned to specifically divert around expected ‘bad ground’, and others took years to complete at great expense. Stephenson’s team, drawing on their experience from the mining industry, did not take this approach and ultimately worked through the unstable ground, albeit with considerable delays and cost increases. This was achieved in part by establishing a large-scale groundwater pumping system, unique for the time, that lowered groundwater levels and stabilised the quicksand, which resulted from a buried channel of glaciofluvial sands, cut into bedrock, that had been missed by trial borings. Steam engines were used to pump from multiple shafts (including four dedicated pumping shafts, off set from the tunnel alignment), with a reported pumping rate of 136 l/s for several months. One unusual feature was the use of flatrod systems to transmit mechanical power horizontally; this allowed a single engine to drive pumps in several different shafts.

Aquifer Susceptibility to Groundwater Pumping in Kediri City, East Java Province, Indonesia

The development of Kediri City in various sectors, such as industry, agriculture, and population growth, also increases water. The utilization of groundwater is still a major mainstay in this area. The utilization of groundwater includes the construction of production wells for irrigation and raw water. The aquifer susceptibility should be considered during groundwater exploitation to minimize a negative impact on the environment. This research aims to analyze the susceptibility of the aquifer to pumping in Kediri City, which is helpful for planning and making decisions in the management of groundwater resources. The determination of aquifer susceptibility is based on aquifer response characteristics, aquifer storage characteristics, allowable subsidence of groundwater level, and depth to the groundwater table. Based on those parameters, it can be concluded that the aquifer susceptibility on groundwater utilization in Kediri City is at moderate and high levels. Areas with moderate aquifer susceptibility are located on the west side of Kediri City, and high aquifer susceptibility is in the middle to the eastern side of Kediri City.

Assessment of hydraulic conductivity improvement due to vibration application at riverbank

Groundwater abstraction is a process of obtaining subsurface water sources for variety purpose of consumption. However, due to long and continuous pumping, the efficiency might decrease because of soil clogging. This decreased can be quantified and reflected as the change of hydraulic conductivity (K) values at the pumping site. This study aims to assess the variability of soil hydraulic conductivity at groundwater pumping site and also to study the effectiveness of vibration method to improve the hydraulic conductivity by comparing the result of before and after vibration is applied. The study was carried out by measuring the K values using slug test at wells MW01 and MW02 with two durations of vibration which were 45 minutes and 60 minutes. The result shows that values of hydraulic conductivity of the soil were found to have increased for both MW0l and MW02 wells. On first trial, the hydraulic conductivity increases for MW0l and MW02 are 16.7% and 39.3% while on second trial, the percentage increases for MW01 and MW02 are 54.3% and 11.1% respectively. Although the change for MW02 decreased for 60 minutes vibration, it can still be noted as there is a positive impact of vibration to the K value and further extensive data collection will be able to provide better assessment. Thus, it has been proven that the vibration method can be effective in reducing the soil clogging effect and also able to improve the hydraulic conductivity of the soil.

Statistical modeling of spatial and temporal vulnerability of groundwater level in the Gaza Strip (Palestine)

The water supply in the Gaza Strip substantially depends on the groundwater resource of the Gaza coastal aquifer. The climate changes and the over-exploiting processes negatively impact the recovery of the groundwater balance. The climate variability is characterized by the decline in the precipitation by −5.2% and an increase in the temperature by +1 °C in the timeframe of 2020–2040. The potential evaporation and the sunshine period are expected to increase by about 111 mm and 5 hours, respectively, during the next 20 years. However, the atmosphere is predicted to be drier where the relative humidity will fall by a trend of −8% in 20 years. The groundwater abstraction is predicted to increase by 55% by 2040. The response of the groundwater level to climate change and groundwater pumping was evaluated using a model of a 20-neuron ANN with a performance of the correlation coefficient (r)=0.95–0.99 and the root mean square error (RMSE)=0.09–0.21. Nowadays, the model reveals that the groundwater level ranges between −0.38 and −18.5 m and by 2040 it is expected to reach −1.13 and −28 m below MSL at the northern and southern governorates of the Gaza Strip, respectively.

Optimization of Groundwater Pumping and River-Aquifer Exchanges for Management of Water Resources

Groundwater pumping influences the rate of River-Aquifer (R-A) exchanges and alters the water budget of the aquifer. Therefore, fulfilling the total water demand of the area, with an optimal pumping rate of wells and optimal R-A exchanges rate, is important for the sustainable management of water resources and aquatic ecosystems. Meanwhile, comparison of the output of different simulation-optimization techniques, which is used for the solution of water resource management problems, is a very challenging task where different Pareto fronts are compared to identify the best results. In the present work, mathematical models were developed to simulate the R-A exchanges for the lower part of the River Ain, France. The developed models were coupled with optimization models in MATLAB environment and were executed to solve the multi-objective optimization problem based on the maximization of pumping rates of wells and maximization of groundwater input into the river Ain through R-A exchanges. The Pareto front developed by different simulation-optimization models was compared and analyzed. The Pareto fronts were juxtaposed based on the convergence, total diversity, and uniformity with the help of different performance metrics like hypervolume, generational distance, inverted generational distance, etc. The impact of different groundwater models based on domain size and boundary conditions was also examined. Results show the dominance of MOPSO over other optimization algorithms and concluded that the maximization of pumping rates significantly changes after considering the R-A exchanges-based objective function. It is observed that the model domain also alters the output of simulation-optimization, therefore the model domain and corresponding boundary conditions should be selected carefully for the field application of management models. ANN models were also developed to deal with the computationally expensive simulation model by reducing the processing time and were found efficient. Keywords: Simulation-Optimization, Multi-Objective optimization, Artificial Neural Network, River-Aquifer exchanges.

Agricultural impacts of sustainable water use in the United States

Governance measures such as restrictions on groundwater pumping and adjustments to sectoral water pricing have been suggested as response strategies to curtail recent increases in groundwater pumping and enhance sustainable water use. However, little is known about the impacts of such sustainability strategies. We investigate the implications of such measures, with the United States (U.S.) as an example. Using the Global Change Analysis Model (GCAM) with state-level details in the U.S., we find that the combination of these two governance measures can drastically alter agricultural production in the U.S. The Southwest stands to lose upwards of 25% of their total agricultural production, much of which is compensated for by production increases in river basins on the east coast of the U.S. The implementation of future sustainable water governance measures will require additional investments that allow farmers to maximize production while minimizing water withdrawals to avoid potentially detrimental revenue losses.

Studying a Subsiding Urbanized Area from a Multidisciplinary Perspective: The Inner Sector of the Sarno Plain (Southern Apennines, Italy)

Defining the origin of ground deformation, which can be a very challenging task, may be approached through several investigative techniques. Ground deformation can originate in response to both natural (e.g., tectonics) and anthropic (e.g., groundwater pumping) contributions. These may either act simultaneously or be somewhat correlated in space and time. For example, the location of structurally controlled basins may be the locus of enhanced human-induced subsidence. In this paper, we investigate the natural and anthropic contributions to ground deformation in the urbanized area of the inner Sarno plain, in the Southern Apennines. We used a multidisciplinary approach based on the collection and analysis of a combination of geomorphological, stratigraphical, structural, hydrogeological, GPS, and DInSAR datasets. Geomorphological, stratigraphical, and structural data suggested the occurrence of a graben-like depocenter, the Sarno basin, bounded by faults with evidence of activity in the last 39 ka. Geodetic data indicated that the Sarno basin also experienced ground deformation (mostly subsidence) in the last 30 years, with a possible anthropogenic contribution due to groundwater pumping. Hydrogeological data suggested that a significant portion of the subsidence detected by geodetic data can be ascribed to groundwater pumping from the alluvial plain aquifer, rather than to a re-activation of faults in the last 30 years. Our interpretation suggested that a positive feedback exists between fault activity and the location of area affected by human-induced subsidence. In fact, fault activity caused the accumulation of poorly consolidated deposits within the Sarno basin, which enhanced groundwater-induced subsidence. The multidisciplinary approach used here was proven to be successful within the study area and could therefore be an effective tool for investigating ground deformation in other urbanized areas worldwide.