Future Water Shortages Research Articles

Exploring the aquifers shaping Italy's sub-urban landscape

This review paper examines the hydrogeological characteristics and challenges of urban groundwater management in ten major Italian cities: Turin, Milano, Padova, Bologna, Roma, Pescara, Napoli, Bari, Catania, and Cagliari. Urbanization has placed significant pressure on groundwater systems, highlighting the need for sustainable management. The study categorizes the cities based on their hydrogeological settings and groundwater uses, identifying key issues such as salinization, industrial contamination, and land subsidence. The findings emphasize the importance of urban local aquifers (ULAs) for drinking water, industry, and ecological support, advocating for integrated urban water management and governance to enhance resilience against future water shortages and climate change impacts.

Hydrological Analysis Before and After Embankment-Raising Project of Agricultural Reservoir Watershed: A Case Study of Suyang Reservoir

We selected the SWAT hydrological model to analyze the hydrological changes before and after an embankment-raising project in agricultural reservoirs. The model was calibrated and validated from 2015 to 2016 using discharge data from the Songsan gauge station, which serves as a watershed outlet that includes the Suyang Reservoir. The dam height of Suyang Reservoir was raised from 13.5 m to 15.1 m, which resulted in a total storage capacity increase from 7.472 million cubic meters to 11.926 million cubic meters. The calibrated model demonstrates an efficiency of 0.9. Scenarios for pre- (2001-2012) and post-embankment raising (2014-2016) were simulated, and the results for various hydrological components (precipitation, runoff, infiltration, evapotranspiration, percolation, soil moisture, groundwater evaporation, and groundwater recharge) were summarized. The model results revealed average precipitation, runoff, infiltration, evapotranspiration, and groundwater recharge for the pre-embankment raising period (2001-2012) as 1,479.3 mm, 864.1 mm, 550.8 mm, 584.2 mm, and 165.0 mm, respectively. For the post-embankment raising period (2014-2016), the simulated values were 1,290.4 mm, 678.0 mm, 494.0 mm, 587.9 mm, and 145.9 mm, respectively. Below-average precipitation during the post-embankment raising period did not have a significant impact on the operation of the agricultural reservoir. The increased reservoir capacity through the embankment-raising project suggests the potential for additional water supply in the face of future water shortages and abnormal drought conditions. Additional research, including the determination of an appropriate water storage rate, will be necessary through long-term investigations and analyses, and climate change scenarios should be incorporated.

A multi-criteria decision framework for circular wastewater systems in emerging megacities of the Global South

Lima faces increasing water stress due to demographic growth, climate change and outdated water management infrastructure. Moreover, its highly centralized wastewater management system is currently unable to recover water or other resources. Hence, the primary aim of this study is to identify suitable wastewater treatment alternatives for both eutrophication mitigation and indirect potable reuse (IPR). For eutrophication mitigation, we examined MLE, Bardenpho, Step-feed, HF-MBR, and FS-MBR. For IPR, we considered secondary treatment+UF + RO + AOP or MBR + RO + AOP. These alternatives form part of a WWTP network at a district level, aiding Lima's pursuit of a circular economy approach. This perspective allows reducing environmental impacts through resource recovery, making the system more resilient to disasters and future water shortages. The methods used to assess these scenarios were Life Cycle Assessment for the environmental dimension; Life Cycle Costing for the economic perspective; and Multi-Criteria Decision Analysis to integrate both the quantitative tools aforementioned and qualitative criteria for social and techno-operational dimensions, which combined, strengthen the decision-making process. The decision-making steered towards Bardenpho for eutrophication abatement when environmental and economic criteria were prioritized or when the four criteria were equally weighted, while HF-MBR was the preferred option when techno-operational and social aspects were emphasized. In this scenario, global warming (GW) impacts ranged from 0.23 to 0.27 kg CO2eq, eutrophication mitigation varied from 6.44 to 7.29 g PO4− equivalent, and costs ranged between 0.12 and 0.17 €/m3. Conversely, HF-MBR + RO + AOP showed the best performance when IPR was sought from the outset. In the IPR scenario, GW impacts were significantly higher, at 0.46–0.51 kg CO2eq, eutrophication abatement was above 98 % and costs increased to ca. 0.44 €/m3.

Can climate knowledge enable Warragamba Dam, Sydney, Australia to be used to manage flood risk?

Dams that serve a dual purpose of water supply and flood mitigation operate to maintain a defined full supply level of water that balances the two conflicting requirements. To optimize the use of available storage space, the full supply level may be adjusted to reflect changing risks of future water shortages and future flood inflows based on known seasonal variations and current observations. The Warragamba Dam in eastern Australia is located upstream of the populated Hawkesbury-Nepean valley which has one of the largest flood exposures in the country. However, the operating protocol of the reservoir does not include provisions to reduce the full supply level of the dam for flood mitigation. Large scale climate indicators that are known to influence the hydroclimate of this region may potentially contain useful information to inform the dual use of this reservoir, but their utility for this purpose has not been studied. Here we explore whether current observations of large-scale climate along with antecedent catchment conditions can be used to estimate the probability of large inflows into the reservoir in the next 3- and 6 months, to aid flood management. We find that the predictors have a substantial influence on the probability of large inflows. The probability differences during opposite predictor phases vary by season and range from 30% to 70%. Our results indicate that considering current climate information to inform dual use of the Warragamba dam has merit.

Modelling the potential of rainwater harvesting to improve the sustainability of landscape and public garden irrigation

Access to water for irrigating amenity landscape and public gardens is under intense pressure due to the rising competition for water between different sectors, exacerbated by increased drought risk and climate change. Rainwater harvesting (RWH) has the potential to reduce the economic impacts of restrictions on irrigation abstraction in dry years and to build resilience to future water shortages. This study investigated the hydrological viability of RWH for the landscape and public garden sector based on an analysis of five Royal Horticultural Society gardens. A RWH model was developed and combined with on-site observations, key informant interviews and GIS analyses, to estimate irrigation demands and the volumes of harvested rainfall for contrasting agroclimatic years. The results showed that gardens located in wetter regions and with low irrigation water demand to harvestable area ratio had a higher RWH potential and could almost exclusively rely on rainwater to meet irrigation demand, even in dry years. RWH potential is more limited for gardens in drier regions where they would require larger areas to harvest rainwater and for storage. Appropriately designed rainwater harvesting systems offer the potential to remove most of the risk of irrigation abstraction restrictions during dry years and associated impacts on amenity planting quality and visitor experience.

Waterworks, municipal government and the environment in twentieth-century Britain

Abstract From the nineteenth century onwards, municipal authorities vested increasing amounts of power in experts, those who could provide specialist knowledge on areas outside the remit of local councillors. This, though, was attached with risk, as municipal resources could be wasted. This article takes the example of the Ure Valley waterworks project, a scheme developed by Leeds Corporation at the start of the twentieth century. What was deemed a necessary and straightforward project to alleviate future water shortages became embroiled in engineering difficulties and financial issues which resulted in only one of the five planned reservoirs being built. This case-study shines a light on the inner workings of local government, as well as the confluence between politics, economics and the urban–rural hinterland environment.

Treatment of urban wastewater by coupling planted filters with anodic oxidation process

ABSTRACT The wastewater reuse strategy has the advantage of providing an effective resource to reduce water deficits, protect natural resources and alleviate future water shortages caused by climate change. In many arid and semi-arid regions, water reuse provides the majority of irrigation water, which is why appropriate treatment techniques are needed. These include planted filters, with restricted reuse of agricultural treated water. The main innovation is therefore to develop a new technique with reduced operating costs and increased efficiency for wastewater treatment that can be used in different sectors (household, industrial, washing centers…). The current work aimed to assess the performance of coupling planted Filters with anodic oxidation on platinum to remove contaminants and pathogens from urban wastewater effluents. To evaluate the efficiency of this hybrid process, urban sewage was first treated by filters planted with reeds, then by anodic oxidation on platinum using photovoltaic panels. Results showed that this treatment system allows a complete elimination of organic matter, ammonium nitrogen, and pathogenic bacteria. Removal rates were ~ 100% for COD, ~100% for BOD, ~100% for NH4 +, 93.24% for NO3 −, and ~100% for TC, FC, and FS. Due to the satisfactory performance, treated water can be reused without restriction in different sectors.

Using Deficit Irrigation Strategies and Organic Mulches for Improving Yield and Water Productivity of Mango under Dry Environment Conditions

Many techniques have been and are being made to find alternatives to water-saving practices. Among them, Partial root drying (PRD), one effective approach, plays a major role in reducing the harmful effects of water deficit stress. Field experiments were carried out on mango trees for a private farm in Egypt over the course of two years, 2020/2021 to 2021/2022, in an area with sandy soil, hot summer conditions, and cold and rainy winter conditions. In the experiment that was carried out, the experimental design included using different irrigation strategies (I1, 100% full irrigation “FI”; I2, 75% FI; I3, 50% FI; and I4 (PRD), 50% FI) in the main plot and different amounts of organic mulch in the soil (L0, no layers of organic soil mulch, used as a control; L1, a single layer of organic soil mulch; L2, two layers of organic soil mulch; and L3, three layers of organic soil mulch) in subplots of the main plot in order to inspect the impact of the treatments on yield, water productivity, and energy usage under arid conditions. To meet the study’s objective, two field experiments were carried out at a private farm. Our results demonstrate a general decrease in water stress and salt accumulation inside the root-zone area with PRD and L3. During the 2020/2021 and 2021/2022 seasons the PRD strategy increased fruit yields by 3.7 and 7.3% and water productivity by 51.9 and 53.1%, respectively, compared with the control treatment (I1) while reducing the amount of applied irrigation water by 50%. The PRD strategy along with organic mulching showed superior results with respect to increasing mango yields and water productivity. In general, PRD can be used as a good technique to save water and energy by up to 50% while enhancing productivity, ultimately improving mango yields under arid climatic conditions. Thus, it may prove a good adaptation strategy for current and future water shortage scenarios involving climate change.

Research on multi-objective optimal allocation of regional water resources based on improved sparrow search algorithm

Abstract Nowadays, the conflict between the supply and demand of water resources in many regions is becoming increasingly prominent. Scientific allocation of regional water resources has become the key to solving the contradiction. In this study, a regional multi-objective water resources optimization allocation model considering social, economic, and ecological objectives is established, and four improvement spots are introduced to the sparrow search algorithm (SSA) to form an improved sparrow search algorithm (ISSA). By testing nine benchmark functions including monotonic and multi-peaked, the search efficiency and average convergence results of ISSA are significantly enhanced compared with other intelligent algorithms. Meanwhile, this research uses Luanchuan County, Henan Province, China, as an example to solve the water resource allocation scheme for 2025 and 2030 in the region using ISSA. The results show that the overall water shortage rate decreases to 3.49 and 2.79%, respectively, under the 75% guarantee rate, resulting in an effective reduction in future water shortages. Simultaneously, the scheme proposed has sound comprehensive benefits and can provide important technical support for the refined management of water resources, which is a reference and guidance for solving the contradiction between water supply and demand at the current stage.

System dynamics simulation and scenario optimization of China's water footprint under different SSP-RCP scenarios

Under the dual influence of socioeconomic development and climate change, water resources in China are under increasing stress. It is of great significance to comprehensively explore the changing trend of China's water footprint (WF) in the future, clarify the water resource challenges that China will face, and alleviate water shortage and water pollution problems. This paper uses System Dynamics (SD) to build a simulation model of China's WF, calculate China's WF from 2000 to 2019, and for the first time, simulate and optimize China's WF from 2020 to 2050 under the SSP-RCP scenario matrix composed of Shared Socioeconomic Pathways (SSPs) and Representative Concentration Pathways (RCPs). The results are as follows. (1) From 2000 to 2019, China's WF increased to 2009 and began to decline. The main contributors are grey WF and agricultural WF. (2) During 2020–2050, China's total WF under the SSP1-2.6 scenario will always be at the lowest; compared with other scenarios, the simulation result of China's total WF under the SSP2-4.5 scenario is the closest to the actual situation in China in 2020, 2021 and 2022. China's total WF under the SSP4-6.0 scenario is close to that under the SSP2-4.5 scenario, but the numerical variation characteristics of the WF composition are different. China's total WF under the SSP3-7.0 and SSP5-8.5 scenarios is high. (3) Based on the changes in WF and water resources supply/demand ratio under different scenarios, the SSP1-2.6 scenario is the best scenario to mitigate a future water shortage and water pollution in China. The research results can help decision-makers formulate relevant management policies and socioeconomic development models for water resource utilization and provide decision support for alleviating water shortages and water pollution in China.

Novel Multi-Channel Coated Silica Based Membranes Applied for Peat Water Ultrafiltration

South Kalimantan-Indonesia is in the Southern part of Borneo which almost half of the population lives in remote areas. Geographically, people are isolated and have poor access to electricity as well as a clean water supply. It is very essential to ensure the availability of clean water produced from peat water to overcome future water shortages. This work performs the fabrication of multi-channel silica-based membranes applied for peat water ultrafiltration which is demonstrated under various transmembrane pressure (TMP) and top layer types. The silica based top layer membranes were fabricated from three different sources (silica-pectin, organosilica, and pure silica) via dipcoating method onto macroporous multi-channel alumina support (4 bore). Peat water was treated by multi-channel membranes through ultrafiltration process through cross flow system. According to the results, all multiples top layer pore size were obtained with range from 2.1 to 6 nm classified as mesoporous membranes. This process exhibited a promising outcome for removal natural organic matter (NOM) about 89-71% (UV254 rejection) at TMP 1-3 bar, respectively. Besides that, normalized permeate fluxes of that membrane excellently stable over 180 min operation time. It is concluded that silica based multichannel membranes are either compatible to treat peat water that has high number of NOM as well as excellent to overcome membrane fouling.

An integrated socio-economic agent-based modeling framework towards assessing farmers’ decision making under water scarcity and varying utility functions

A spatio-temporal Agent Based Modeling (ABM) framework is developed to probabilistically predict farmers' decisions concerning their future farming practices when faced with potential water scarcity induced by future climate change. The proposed framework forecasts farmers' behavior assuming varying utility functions. The functionality of the proposed ABM is illustrated in an agriculturally dominated plain along the Eastern Mediterranean coastline. The model results indicated that modelling farmers as agents, who were solely interested in optimizing their agro-business budget, was only able to reproduce 35% of the answers provided by the farmers through a administered field questionnaire. Model simulations highlighted the importance of representing the farmers' combined socio-economic attributes when assessing their future decisions on land tenure. This approach accounts for social factors, such as the farmers' attitudes, subjective norms, social influence, memories of previous civil unrest and farming traditions, in addition to their economic utility to model farmer decision making. Under this scenario, correspondence between model simulations and farmers' answers reached 95%. Additionally, the model results show that when faced with the negative impacts of climate change, the majority of farmers seek adaptive measures, such as changing their crops and/or seeking new water sources, only when future water shortages were predicted to be low to moderate. Most opt to cease farming and allow their lands to urbanize or go fallow, when future water shortages were predicted to be high. Meanwhile, incorporating and modeling the social influence structures within the ABM diminished farmers' willingness to adapt and doubled their propensity to sell or quit their land. The proposed framework is able to account for a variety of utility functions and to successfully capture the actions and interactions between farmers and their environment; thus, it represents an innovative modeling approach for assessing farmers’ behavior and decision-making in the face of future climate change. The nonspecific structure of the framework allows its application at any agriculturally dominated setting facing future water shortages promulgated by a changing climate.

Risk-aversion optimal hedging scenarios during droughts

The primary purpose of a water supply reservoir is to regular highly fluctuating streamflow for providing reliable water supplies. Reducing water shortage risk for impending droughts is a challenge task in real-time reservoir operation due to future inflow uncertainty. The main aim of this study is to propose risk-aversion optimal hedging scenarios during droughts, which is achieved by a two-stage approach. The water shortage probabilities of future lead times are analytically estimated first, then follows an optimization framework that simultaneously minimizing water shortage probabilities of future lead times and sustaining long-term water supply reliability. With an illustration application of the Nanhua Reservoir located in southern Taiwan, the results indicate that the proposed optimization framework provides an efficient hedging to reduce future water shortage probabilities and mitigate severe water shortages in real-time operation. The proposed optimal hedging scenarios outperforms the rule-curve-based current operation. Further improvements are noted for the time-varying rationing coefficient scenarios than the constant-coefficient scenario and the most favorable scenario is the scenario with the highest time-varying frequency. Using the storage to trigger hedging associated with estimated future lead-time water shortage probabilities as the objective functions, the proposed optimal hedging scenarios are not only risk aversion but also executable in real-time operation during droughts.

Improved feed forward with bald eagle search for conjunctive water management in deficit region

Due to increasing requirements on water resources and a lower recharge rate, the farming seasons are a vital season for the management of groundwater and surface water resource management. This condition necessitates the use of combined water distribution to meet the full water requirements. Analysis of existing surface water resources and related restrictions, this research suggested an algorithm for aquifer stabilization and fulfilling optimum water requirements. To manage the optimum withdrawals and the subsequent drop, this technique first employed the MODFLOW model for simulating the water levels. Next, an improved feed-forward neural network (IFFNN) was combined with an optimization method to create a machine learning (ML) framework. During the last phase, the findings of the optimized connectives approach as well as the relevant fields technologies to determine using improved bald eagle search with least square SVM(IBES-LSSVM) method that predicted the level of water deficit for every period, especially during farming seasons. This approach is based on an improved bald eagle search (IBES) optimization technique for finding the best settings for a least-squares support vector machine (LSSVM). The findings revealed that between 2005 and 2020, the year with the biggest water deficit was 2018 when only roughly 64 percent of water need was satisfied by groundwater (69 percent) and surface water (64 percent) (33 percent). The water depth may have risen by around 0.7 m during the study period if the optimum model had been used. The outcome of this research will help the management forecast future water shortages and make smarter water strategic choices.

Effects of land-use change on the volume of water flow into the Mun Bon reservoir in Nakhon Ratchasima Province, Thailand

The land-use patterns in watershed areas in the Chorakhe Hin Sub-district, Khon Buri District, Nakhon Ratchasima Province, Thailand, have been found to change from forest areas. Different agricultural areas cause variations in the amount of water that flows from the stream into the reservoir, potentially leading to future water shortages. This study was conducted to explore the effects of land-use change on the volume of water flow into the Mun Bon Reservoir, Chorakhe Hin Sub-district, Khon Buri District, Nakhon Ratchasima Province, Thailand. The model analysis techniques, namely Markov’s Chain CLUES and SWAT, were employed to predict the effects of land-use patterns in the area of the upper Mun River on the volume of water flow into the Mun Bon reservoir. According to the predictions obtained based on the land-use models, forest areas may be converted into cassava plantations by 2029. When the comparative effects were considered, the normal volume of water flowing into the Mun Bon reservoir was found to be equivalent to 96 million cubic meter per year. The predicted volume before Christ (A.D.) 2029 is 30 million cubic meter. Accordingly, the water volume in the Mun Bon reservoir would be lower than that derived from the usual land-use patterns.

A multistage distributionally robust optimization approach to water allocation under climate uncertainty

This paper investigates a Multistage Distributionally Robust Optimization (MDRO) approach to water allocation under climate uncertainty. The MDRO is formed by creating sets of conditional distributions (called conditional ambiguity sets) on a finite scenario tree. The distributions in the conditional ambiguity sets remain close to a nominal conditional distribution according a ϕ-divergence (e.g., Kullback-Leibler divergence, Hellinger distance, Burg entropy, etc.). The paper discusses a decomposition algorithm to solve the resulting MDRO with ϕ-divergences, which uses the dual formulation and solves only linear subproblems instead of convex ones. Some properties of the algorithm such as generating feasible policies and valid upper/lower bounds are established. The paper then applies the modeling and solution techniques to allocate water in a rapidly-developing area of Tucson, Arizona. Tucson, like many arid and semi-arid regions around the world, faces considerable uncertainty in its ability to provide water for its citizens in the future. The primary sources of uncertainty in the Tucson region include (1) unpredictable population growth, (2) the availability of water from the Colorado River, and (3) the effects of climate variability on water consumption. This paper integrates forecasts for all these sources of uncertainty into a single optimization model for robust and sustainable water allocation. Then, it uses this model to analyze the value of constructing additional treatment facilities to reduce future water shortages. The results indicate that the MDRO approach can be very valuable for water managers by providing insights to minimize their risks and help them plan for the future.

Agricultural Water Optimal Allocation Using Minimum Cross-Entropy and Entropy-Weight-Based TOPSIS Method in Hetao Irrigation District, Northwest China

Affected by the temporal and spatial changes of natural resources, human activities, and social economic system policies, there are many uncertainties in the development, utilization, and management process of irrigation district agricultural water resources, which will increase the complexity of the use of irrigation district agricultural water resources. Decision makers find it challenging to cope with the complexity of fluctuating water supplies and demands that are critical for water resources’ allocation. In response to these issues, this paper presents an optimization modeling approach for agricultural water allocation at an irrigation district scale, considering the uncertainties of water supply and demand. The minimum cross-entropy method was used to estimate the parameters of hydrologic frequency distribution functions of water supply and demand, which are the basis for agricultural water resources’ optimal allocation and the evaluation of water resources’ carrying capacity in the Hetao Irrigation District. Interval Linear Fractional Programming was used to find water availability, shortage, and use efficiency in different irrigation areas of the Hetao Irrigation District (HID) under different scenarios. The denominator of fractional planning is the environmental goal, and the numerator is the economic goal; so, the objective function of fractional programming is the utility rate required in the post-optimization analysis. Future water availability and shortage scenarios are adopted consistent with the Representative Concentration Pathways’ (RCPs’) framework, and future water use scenarios are developed using the Shared Socioeconomic Pathways’ (SSPs’) framework. Results revealed that under SSP1, the annual water consumption increased from 30 billion m3 to 60 billion m3, almost doubling in Urad. The annual water consumption under SSP2 and SSP3 increased slightly, from 30 billion m3 to about 50 billion m3. The amount of water available for well irrigation in Urad decreased from 300 to 250 billion m3, while the amount of water available for canal irrigation in Urad remained at 270 billion m3 from 2010 s to 2030 s, only dropping to 240 billion m3 in 2040 s. The entropy-weight-based Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) method was applied to evaluate agricultural water resources’ allocation schemes because it can avoid the subjectivity of weight determination and can reflect the dynamic changing trend of irrigation district agricultural water resources’ carrying capacity. The approach is applicable to most regions, such as the Hetao Irrigation District in the Upper Yellow River Basi with limited precipitation, to determine water strategies under the changing environment.

Water shortage risk in Taiwan’s Silicon Valley

ABSTRACT Hsinchu is Taiwan’s Silicon Valley and is an important part of the world’s technology industry, but there is a risk of water shortages in the area. Some of Hsinchu’s water supply is currently taken from neighboring areas. This study determines the risk to Hsinchu’s water supply and proposes solutions to water shortages. Five scenarios are used to determine the risk to the water supply. The simulation of the water resources system for this study uses historical daily flow data from 1969 to 2017 in the river basin. To reduce the risk of future water shortages in Hsinchu, the existing external support (up to 120,000 m3/day) must be maintained, and the Hsinchu area should be prioritized over the needs of the local agricultural industry in terms of water supply. This strategy would increase the water transfer volume of the Touqian River Basin by 36.83 million cubic meters per year. The results show that the water rights transfer program will address water shortages in Hsinchu. If the government’s agriculture, economic and water departments are assertive, this plan is feasible and will not be difficult to implement.

Linkages between land-use change and groundwater management foster long-term resilience of water supply in California

Study RegionWe created a 270-m coupled model of land-use and groundwater conditions, LUCAS-W[ater], for California’s Central Coast. This groundwater-dependent region is undergoing a dramatic reorganization of groundwater management under California’s 2014 Sustainable Groundwater Management Act (SGMA). Study FocusUnderstanding land-use and land-cover change supports long-term sustainable water management. Anthropogenic water demand has depleted groundwater aquifers worldwide, while future water shortages will likely affect land-use change, creating system feedbacks. Our novel participatory approach fused changes in land-use and associated water use from county-scale data to local water agencies’ estimates of total sustainable supply, scaling up local hydro-geologic knowledge from heterogeneous aquifers and diverse management approaches to a regional level. We assessed five stakeholder-driven scenarios with the same historic rates of urban and agricultural land-use change, but different water and land-use management, analyzing how management strategies altered both the spatial pattern of development and subsequent water sustainability from 2001 to 2061. New Hydrological Insights for the RegionTransformative strategies using demand-side interventions that coupled water availability to land-use more effectively achieved long-term sustainability than adaptive strategies using supply-side interventions to increase water supplies. Limiting water withdrawals within SGMA regulated basins resulted in leakage of development into unregulated basins, increasing groundwater pumping there. Protecting ecosystems, farmlands, and recharge areas from development reduced leakage into undeveloped basins without negatively affecting water sustainability.

Adaptive responses of freshwater pearl mussels, Margaritifera margaritifera, to managed drawdowns

Abstract Alterations to water management practices, in response to a growing demand to maximize energy production from renewable sources, threaten to exacerbate anticipated future water shortages caused by severe drought episodes, brought on by climate change. Across Scotland, many highly managed systems are inhabited by some of the last remaining reproductively viable populations of the freshwater pearl mussel, Margaritifera margaritifera. A lack of empirical evidence concerning mussel responses to alterations in flow is inhibiting the development of effective conservation management practices to prolonged drought. This study addressed this knowledge gap by examining the response of M. margaritifera to controlled water level drawdowns in laboratory and field settings. Using a laboratory flume, the responses of M. margaritifera from two different populations (a regulated system versus an unregulated system) were compared across rates of drawdown and density treatments. An analogous field trial was undertaken to examine the responses of M. margaritifera in a regulated system, with a hydroelectric dam facilitating a controlled drawdown. The study showed that M. margaritifera can detect alterations in flow depth, which culminate in the emersion of mussel beds, and respond by undertaking vertical and horizontal movements to mitigate the risk of prolonged aerial exposure. Results from the field trial corroborated findings from the flume experiments, with 80% of mussels shown to avoid emersion successfully by tracking receding water levels. Findings from this study support the role of controlled drawdowns in regulated rivers to reduce mortalities associated with receding water levels during prolonged low‐flow episodes. Differences between populations in response highlight a need to adopt a context‐dependent approach to conservation efforts.