A trophic model for the Danshuei River Estuary, a hypoxic estuary in northern Taiwan

The estuary of the Danshuei River, a hypoxic subtropical estuary, receives a high rate of untreated sewage effluent. The Ecopath with Ecosim software system was used to construct a mass-balanced trophic model for the estuary, and network analysis was used to characterize the structure and matter flow in the food web. The estuary model was comprised of 16 compartments, and the trophic levels varied from 1.0 for primary producers and detritus to 3.0 for carnivorous and piscivorous fishes. The large organic nutrient loading from the upper reaches has resulted in detritivory being more important than herbivory in the food web. The food-chain length of the estuary was relatively short when compared with other tropical/subtropical coastal systems. The shortness of food-chain length in the estuary could be attributed to the low biomass of the top predators. Consequently, the trophic efficiencies declined sharply for higher trophic levels due to low fractions of flows to the top predators and then high fractions to detritus. The low biomass of the top predators in the estuary was likely subject to over-exploitation and/or hypoxic water. Summation of individual rate measurements for primary production and respiration yielded an estimate of −1791 g WW m⁻² year⁻¹, or −95 g C m⁻² year⁻¹, suggesting a heterotrophic ecosystem, which implies that more organic matter was consumed than was produced in the estuary.     

Environmental Effect Caused by Over-exploitation of Deep Groundwater in North China

Based on the formation and development analysis of the environmental geological disaster of land subsidence, earth fissures and other geological disasters in the North China, it showed these disasters caused a very serious problem in some areas of the North China, such as the deep groundwater exploitation cone, which is accumulated with great damage and loss and is hard to be controlled, therefore, great attention should be paid. It is considered that the formation of the deep groundwater cone is the root of various geological environmental problems, and the groundwater cone recovery is the key to solve other environmental problems     

Participatory groundwater management in Jordan: Development and analysis of options

Groundwater over-exploitation has been on the rise in Jordan. Competing demands have grown in the face of perennial water shortages, a situation which has been exacerbated by drought conditions in the past decade. This paper reports findings of a project in which management options to address over-exploitation were developed for one of Jordans principal aquifer systems, the Amman-Zarqa Basin. Options for addressing the situation were developed through a participatory approach that involved government officials and various public and private sector interest groups. Particular efforts were made to involve well irrigators, who are likely to be heavily impacted by the changes required to reduce groundwater pumping to a sustainable level. With information obtained from a rapid appraisal survey as well as from interviews with farmers, community groups, government officials, and technical experts, an extensive set of options was identified for evaluation. Based on integrated hydrogeologic, social, and economic analysis, five complementary management options were recommended for implementation. These included the establishment of an Irrigation Advisory Service, buying out farm wells, placing firm limits on well abstraction and irrigated crop areas, exchanging treated wastewater for groundwater, and measures to increase the efficiency of municipal and industrial water use. Various combinations and levels of these options were grouped in scenarios, representing possible implementation strategies. The scenarios were designed to assist decision makers, well owners and other stakeholders in moving gradually towards a sustainable abstraction regime. Social and economic aspects of each option and scenario were analyzed and presented to stakeholders, together with a summary of legal, institutional and environmental ramifications. Combining scientific analysis with a participatory approach in the Amman Zarqa Basin groundwater management was devised as a prototype to be used in the management of other groundwater basins in Jordan. This participatory management approach would also be useful in other parts of the world that are experiencing similar groundwater over-exploitation problems.Résumé La surexploitation des eaux souterraines prend de limportance en Jordanie. Les demandes en concurrence ont augmenté face à des déficits permanents deau, situation qui a été exacerbée par la sécheresse de la dernière décennie. Cet article rend compte de laboutissement dun projet dans lequel des options de gestion portant sur la surexploitation ont été développées pour lun des principaux systèmes aquifères de Jordanie, le bassin dAmman Zarqa. Des options pour aborder cette situation ont été développées grâce à une approche participative qui implique des fonctionnaires du gouvernement et des groupes dintérêts variés des secteurs public et privé. Des efforts particuliers ont été faits pour impliquer les irrigants utilisant des puits, qui sont probablement ceux qui ont le plus fort impact sur les changements attendus permettant de remettre le système en équilibre. À partir des informations obtenues de campagnes rapides dévaluation, telles que des réunions de communautés et des entrevues avec des experts techniques du gouvernement, un large jeu doptions a été identifié pour lévaluation. Basées sur une analyse hydrogéologique, sociale et économique, cinq options complémentaires de gestion ont été recommandées pour la réalisation. Ce sont la création dun Service Consultatif dIrrigation, achetant les puits agricoles, fixant des limites fermes aux prélèvements des puits et aux zones irriguées, échangeant les eaux usées traitées avec des eaux souterraines, et la mise en place de mesures pour accroître lefficacité des usages collectifs et industriels. Des combinaisons et des niveaux variés de ces options ont été regroupés en scénarios, présentant les stratégies possibles de mise en uvre. Les scénarios ont été mis au point pour assister les décideurs, les propriétaires de puits et les autres acteurs pour atteindre progressivement un régime de prélèvement durable. Les aspects sociaux et économiques de chaque option et de chaque scénario ont été analysés et présentés aux acteurs, en même temps quun résumé des ramifications légales, institutionnelles et environnementales. En combinant une analyse scientifique à une approche participative du bassin dAmman Zarqa, la gestion des eaux souterraines a été imaginée comme un prototype pouvant être utilisé pour la gestion dautres bassins aquifères de Jordanie. Il peut également être utile à dautres régions du monde qui sont concernées par des problèmes similaires de surexploitation des eaux souterraines.Resumen La sobreexplotación de las aguas subterráneas ha ido en aumento en Jordania, donde las demandas en competición han crecido frente a una escasez perenne de agua, situación que ha sido agravada por el estado de sequía de la última década. Este artículo presenta los hallazgos de un proyecto en el que se han desarrollado opciones de gestión para hacer frente a la sobreexplotación en uno de los principales sistemas acuíferos de Jordania: la cuenca de Ammán-Zarga. Se ha elaborado opciones para afrontar la situación mediante un enfoque participativo que incluye a personal del gobierno y a diversos grupos de interés de los sectores público y privado. En particular, se ha intentado involucrar a los regantes que se sirven de aguas subterráneas, quienes tienen más probabilidad de ser directamente afectados por los cambios requeridos para devolver el sistema a un balance equilibrado. A partir de la información obtenida en rápidas campañas de valoración, así como de encuentros con la comunidad y entrevistas con los expertos técnicos del gobierno, se ha identificado un amplio conjunto de opciones para su evaluación. Basándose en un análisis integrado de los aspectos hidrogeológicos, sociales y económicos, se ha recomendado la implementación de cinco opciones complementarias de gestión: establecimiento de un Servicio Asesor de Riego; adquisición de pozos de granjas; imposición de límites estrictos en las extracciones de pozos y superficies de riego; substitución de las aguas subterráneas con aguas residuales depuradas; y medidas para incrementar la eficiencia de los usos municipales e industriales del agua. Se ha agrupado varias combinaciones y niveles de dichas opciones en escenarios, representando estrategias posibles de implementación. Los escenarios han sido diseñados para ayudar a los gestores en la toma de decisiones, a los propietarios de pozos y a otros agentes para que se vaya consiguiendo de forma gradual un régimen de extracciones sustentable. Se ha analizado los aspectos sociales y económicos de cada opción y de cada escenario, presentándolos a los diversos agentes, además de generar un resumen de ramificaciones legales, institucionales y medioambientales. Se ha concebido la combinación de un análisis científico con un enfoque participativo en la cuenca de Ammán-Zarga como un prototipo de gestión de las aguas subterráneas que puede ser aplicado a la gestión de otras cuencas en Jordania. También sería útil en otros lugares del mundo que estén experimentando problemas similares de sobreexplotación de los recursos hídricos subterráneos.Abbreviations and acronyms AED Academy for Educational Development - ARD Associates in Rural Development - AZB Amman–Zarqa Basin - ECC Economic Consultative Council - GMCC Groundwater Management Consultative Committee - GMF Groundwater Management Fund - GIS Geographic Information System - HDH Hashmiya–Dulayl–Hallabat - IAS Irrigation Advisory Service - JICA Japanese International Cooperation Agency - M&I Municipal and Industrial - MOA Ministry of Agriculture - MWI Ministry of Water and Irrigation - NCARTT National Center for Agricultural Research and Technology Transfer - NGO Non-governmental Organization - O&M Operations and Maintenance - RA Rapid Appraisal - RS Remote Sensing - UFW Unaccounted for Water - USAID United States Agency for International Development - WAJ Water Authority of Jordan - WEPIA Water Education & Public Information Activity - WRPS Water Resource Policy Support     

Dynamic process analyses of saline intrusion with over-exploitation by coupled flow and dispersive modelling

Understanding of saline intrusion into coastal aquifer is an important issue in management and protection of groundwater resource, which can be well achieved by groundwater modelling. To explain some phenomena of correlation between groundwater level and salinity in observation wells in coastal area, the authors compare the migration velocity of saline particles and transmission velocity of water pressure and derive analytical equations of these two velocities for plane and radial flows. The driving force and resistance of saline intrusion were analysed based on the analytical modelling. The destruction and reconstruction of the equilibrium between fresh water seepage towards sea and saline dispersion to inland were considered as an essence of whole intrusion process. The dynamic process of seepage and dispersion at different stages of saline intrusion were analysed under groundwater over-exploitation. The basic equations of saline intrusion were derived and the mechanism of transitional zone movement was discussed. These constitute coupled seepage–dispersion theory of saline intrusion, which becomes an important supplement to existing theory of saline intrusion. As a case study on saline intrusion in Guangrao County in Eastern China, this theory was applied to predict the development of saline intrusion in the study area.     

Recovery scenarios for deep over-exploited aquifers with limited recharge: methodology and application to an aquifer in Belgium

Recharge of deep-seated aquifers must be provided through leakage from overlying geological formations and can be very limited. Although hydraulic characteristics of these aquifers may be favorable for extensive exploitation, the renewability of the groundwater resource may be very restricted and only significant on long time scales. Over-exploitation of such aquifers leads to steadily declining piezometric levels and water balancing and steady state conditions are not to be expected on the short term. Recovery of such systems is very difficult, also because of the socio-economic dependencies of the water resource and the long time it requires to replenish the system. Management plans for restoration should be based on the transient hydrodynamical behaviour. A recovery plan should be developed based on results of a groundwater flow model. In a first step must be simulated how long it will take for the aquifer system to fully recover by natural recharge. As this will most often be a very long time it can be cancelled out as a realistic scenario. An alternative objective is to be formulated which could be achieved in the near future on a time scale of years or decades. Using model simulations, reduction schemes of exploitation rates shall be quantified that will allow to reach these defined goals, such as raising piezometric levels above the top of the aquifer itself or above the top of the overlying geological unit. The methodology is illustrated with an example of a deep hard rock aquifer in Belgium where piezometric levels have dropped below the top. The objective here was to raise the levels again above the top within the next 50 years. However, this is not accomplished by balancing aquifer recharge and discharge, but is reached by a lateral redistribution of the water over the aquifer extent. A full recovery of this aquifer would require at least a century with only a very limited amount of exploitation.     

Groundwater quality in a coastal area: a case study from Andhra Pradesh, India

Over-exploitation of groundwater results in decline of water levels, leading to intrusion of salt water along the coastal region, which is a natural phenomenon. A groundwater quality survey has been carried out to assess such phenomena along the coast of Visakhapatnam, Andhra Pradesh, India. Brackish groundwaters are observed in most of the wells. The rest of the wells show a fresh water environment. The factors responsible for the brackish groundwater quality with respect to the influence of seawater are assessed, using the standard ionic ratios, such as Ca²⁺:Mg²⁺, TA:TH and Cl⁻:HCO⁻ ₃. Results suggest that the brackish nature in most of the groundwaters is not due to the seawater influence, but is caused by the hydrogeochemical process. Some influence of seawater on the groundwater quality is observed along the rock fractures. The combined effect of seawater and urban wastewaters is due to the inferior quality of groundwater in a few wells, where they are at topographic lows close to the coast.     

Groundwater resources and quality in northeastern Jordan: safe yield and sustainability

Over-abstraction of groundwater is one concern of the Badia Research and Development Programme. The upper aquifer of the Azraq basin forms the largest resource of good-quality water, but current abstraction exceeds both average recharge and the safe yield of the aquifer, which is over-exploited. Although there has been no deterioration in water quality and only minor drawdown, the springs at Azraq have dried up, with severe, undesirable environmental impacts. Total abstraction of 20 × 10⁶ m³ yr⁻¹ appears to be sustainable and would allow some springflow, but this leaves a shortfall of 40 × 10⁶ m³ yr⁻¹ for domestic supply and agriculture.     

Assessment of water level threshold for groundwater restoration and over-exploitation remediation the Beijing-Tianjin-Hebei Plain

The Beijing-Tianjin-Hebei Plain (BTHP) is the political, economic and cultural center of China, where groundwater is the main source of water supply to support social and economic development. Continuous overdraft of the resources has caused a persistent decline of groundwater level and formed a huge cone of depression at a regional scale. This paper addresses current groundwater situation over the BTHP area. The paper also delineates the groundwater flow field, using groundwater level data, in order to provide an effective method for the restoration of groundwater level and associated water resources management. Based on the analysis of multiple factors, such as groundwater level, soil salinization, ground subsidence, groundwater recharge and storage, urban underground space security, formation of fractures, and seawater intrusion, the threshold for groundwater level restoration is defined, and some measures for groundwater over-exploitation management are accordingly proposed. The study shows that: (i) Since the 1980s to 2020, shallow groundwater level in the western part of the BTHP area has dropped by 25 m to 60 m, while the cumulative decline of deep groundwater in the central and eastern regions is in the range of 40–80 m; (ii) The water table of the shallow groundwater within the depression zone over the Western Piedmont Plain should be controlled in the range of 15–30 m below ground level (mbgl), while the depth of groundwater level in large and medium-sized urban areas should be controlled within 20–30 mbgl. The groundwater level in the resource preservation area should be controlled within 10–15 mbgl, and the groundwater level in the area with identified soil salinization in the central and eastern plain should be controlled within 3–10 mbgl. However, for the deep groundwater in the central and eastern plainwater, the main focus of the resources management is to control the land subsidence. The water level in the severe land subsidence area should be controlled within 45–60 mbgl, and in the general subsidence area should be controlled within 30–45 mbgl; (iii) Based on the water level recovery threshold and proposed groundwater overdraft management program, if the balance of abstraction and recharge is reached in 2025, the shallow groundwater abstraction needs to be gradually reduced by about 2×10⁸ m³. Meanwhile, the ecological water replenishment of rivers through the South-to-North Water Transfer Project should be increased to 28.58×10⁸ m³/a, and the deep groundwater abstraction needs to be gradually reduced by 2.24×10⁸ m³. To reach the target of shallow groundwater level in 2040, surface water replacement is recommended with a rate of 25.77×10⁸ m³/a and the ecological water replenishment of rivers in the South-to-North Water Diversion Project should reach 33.51×10⁸ m³/a. For deep groundwater recovery, it is recommended to replace the deep freshwater extraction with the utilization of shallow salt water by 2.82×10⁸ m³ , in addition to the amount of 7.86×10⁸ m³ by water diversion. The results are of great significance to the remediation of groundwater over-exploitation, the regulation of water resources development and utilization, and ecological protection in Beijing-Tianjin-Hebei plain.