Estimation of Spatial and Temporal Groundwater Balance Components in Khadir Canal Sub-Division, Chaj Doab, Pakistan

Evaluation of the spatial and temporal distribution of water balance components is required for efficient and sustainable management of groundwater resources, especially in semi-arid and data-poor areas. The Khadir canal sub-division, Chaj Doab, Pakistan, is a semi-arid area which has shallow aquifers which are being pumped by a plethora of wells with no effective monitoring. This study employed a monthly water balance model (water and energy transfer among soil, plants, and atmosphere)—WetSpass-M—to determine the groundwater balance components on annual, seasonal, and monthly time scales for a period of the last 20 years (2000–2019) in the Khadir canal sub-division. The spatial distribution of water balance components depends on soil texture, land use, groundwater level, slope, and meteorological conditions. Inputs for the model included data on topography, slope, soil, groundwater depth, slope, land use, and meteorological data (e.g., precipitation, air temperature, potential evapotranspiration, and wind speed) which were prepared using ArcGIS. The long-term average annual rainfall (455.7 mm) is distributed as 231 mm (51%) evapotranspiration, 109.1 mm (24%) surface runoff, and 115.6 mm (25%) groundwater recharge. About 51% of groundwater recharge occurs in summer, 18% in autumn, 14% in winter, and 17% in spring. Results showed that the WetSpass-M model properly simulated the water balance components of the Khadir canal sub-division. The WetSpass-M model’s findings can be used to develop a regional groundwater model for simulation of different aquifer management scenarios in the Khadir area, Pakistan.

Coupled effects of observation and parameter uncertainty on urban groundwater infrastructure decisions

Urban groundwater management requires complex environmental models to represent interactions between hydrogeological processes and infrastructure systems. While the impacts of external uncertainties have been widely studied, there is limited understanding of how decision support is altered by endogenous uncertainties arising from model parameters and observations used for calibration. This study investigates (1) the importance of observation choice and parameter values on aquifer management objectives when controlling for model error, and (2) how the relative performance of management alternatives varies when exposed to endogenous uncertainties, individually and in combination. We use a spatially distributed groundwater model of the Valley of Mexico, where aquifer management alternatives include demand management, targeted infiltration, and wastewater reuse. The effects of uncertainty are evaluated using global sensitivity analysis, performance ranking of alternatives under a range of human-natural parameters, and identification of behavioral parameter sets filtered with an error metric calculated from varying subsets of observations. Results show that the parameters governing hydraulic conductivity and total water use in the basin have the greatest effect on management objectives. Model errors are not necessarily controlled by the same parameters as the objectives needed for decision-making. Additionally, observational and parameter uncertainty each play a larger role in objective variation than the management alternatives themselves. Finally, coupled endogenous uncertainties have amplifying effects on decision-making, leading to larger variations in the ranking of management alternatives than each on their own. This study highlights how the uncertain parameters of a physically-based model and their interactions with uncertain observations can affect water supply planning decisions in densely populated urban areas.

A density-dependent multi-species model to assess groundwater flow and nutrient transport in the coastal Keauhou aquifer, Hawai‘i, USA

Fresh groundwater is a critical resource supporting coastal ecosystems that rely on low-salinity, nutrient-rich groundwater discharge. This resource, however, is subject to contamination from point- and nonpoint-sources such as on-site sewage disposal systems (OSDS) and urban developments. Thus, the significance of flow and transport processes near the coastline due to density effects and water circulation in a complex hydrogeologic system was investigated. A three-dimensional, density-dependent groundwater model was developed for the Keauhou basal aquifer (Hawai‘i Island, USA), where hydraulic head, salinity, nutrient concentrations, and submarine spring flux rates were used as calibration variables to best constrain parameters and produce a comprehensive aquifer management tool. In contrast, a freshwater-only model failed to properly simulate nutrient transport, despite the reasonable success in calibrating hydraulic head measurements. An unrealistic value for hydraulic conductivity was necessary for freshwater-only calibration, proving that hydraulic conductivity is a process-based variable (i.e., depends on model conceptualization and the simulated processes). The density-dependent model was applied to assess relative contaminant source contributions, and to evaluate aquifer response concerning water levels and quality due to changing environmental conditions. Nutrients detected in the aquifer are primarily sourced from OSDS, which was supported by a nitrogen isotope mixing model. Additionally, effects of sea-level rise emphasized the complexity of the study site and the importance of model boundaries. While the model is developed and applied for West Hawai‘i, the adapted approaches and procedures and research findings are applicable to other coastal aquifers.

Salinity-Based Spatial Evaluation of Groundwater Quality for Agricultural Use

The Miandoab Plain has the largest water reserve in the province of West Azerbaijan, northwest Iran. Groundwater resources along with surface-water meet the needs of urban, industrial, and agricultural sectors, and therefore, their quality should be examined. Water quality indices are useful tools for aquifer management. In this research, the groundwater quality of the Miandoab Plain for agricultural purposes was investigated. For this purpose, the concentrations of the ions Mg2+, Ca2+, Na+, Hco3-, So42-, Cl- and the pH level were measured. The indices effective salinity and potential salinity as well as sodium adsorption ratio and electrical conductivity were analyzed to evaluate the salinity. The geostatistical analysis was performed using the GS+ software, and the zoning maps of salinity hazard were prepared using ArcGIS. To prepare the maps, EC, ES, PS, and SAR as well as Mg2+, Ca2+, Na+, Hco3-, So42, and Cl- were selected based on the semi-variogram values ​​and cross-validation technique. The Cl- map was considered as the basis for preparing the groundwater quality maps of the region. The results showed that the groundwater quality in the east of the plain is suitable, in the central part can be recommended under constant supervision, and in the west is unsuitable for agriculture. In other words, according to the geography of the plain, the recharge area is the low-risk part of the plain and the salinity hazard increases toward the discharge area. The results can pave the way for the relevant organizations to plan for the agricultural and environmental sectors.

An Integrated Aquifer Management Approach for Aridification-Affected Agricultural Area, Shengeldy-Kazakhstan

Ongoing water-resource depletion is a common trend in southeastern Kazakhstan and in most of Central Asia, making the use of drainage water for freshwater preservation and groundwater recharge a key strategy for sustainable agriculture. Since the Ily River inflow began to decrease, groundwater levels in the Shengeldy study area site have fallen below the drainage pipes. As such, our main research hypothesis was that owing to drainage infiltration, the regional shallow aquifer can be used as an effective additional water source for moistening crop root systems during the irrigation period. The MODFLOW groundwater flow model was used to simulate and quantitatively assess the combined hydrogeological and irrigation conditions of artificial groundwater recharge both from the subsurface drainage and as an additional source for irrigation. The field study showed that the additional groundwater table elevation will reach approximately 1.5 m under the field drainage system and that the additional groundwater recharge influence zone will develop up to 300–350 m from the drains. The MODFLOW simulation together with full-scale experimental studies suggests that under certain conditions drainage water can be applied both as an additional source of irrigation and for aquifer sustainable maintenance.

Public Participation for Integrated Groundwater Management: The Case of Maneadero Valley, Baja California, Mexico

There is a controversy in groundwater management: some people argue that public participation has decreased efficiency in decision-making, while others believe this process is not executed effectively. Questions about whether public participation results from the context involving influential people, the rules, or the way participation mechanisms were designed need examination. In this study, opportunities, barriers, and challenges of public participation were analyzed in the management of a coastal aquifer affected by marine intrusion in the Maneadero Valley, México. Mixed methods were implemented, involving 28 interviews with key actors and 50 surveys conducted during 2014 and 2017 with groundwater users. Results show that public participation is mainly determined by power differences, lack of continuity in the participatory processes, and the design of the participation mechanisms. State actors have greater decision-making power in integrated groundwater management. In contrast, groundwater users have limited participation in the process of making proposals, and their participation is generally passive. There are limitations to broad, informed, and responsible public participation: examples of these limitations include different levels of information, inappropriate institutional arrangements, failure to disseminate scientific information, lack of spaces to exercise public participation, and absence of political will. Hence, to improve Maneadero aquifer management, it is necessary to decentralize decision-making, integrate technical and non-technical knowledge, generate scientific evidence about water availability, and give a prominent role to stakeholders and users from the initial stages. In addition, internalization and water culture are required. These results can help to guide integrated groundwater management in other arid regions.

Managing coastal aquifers in climate and socio-economic change: An indicator-based multi-criteria decision system approach

<p>Worldwide, climate change as well as socio-economic changes are increasing pressure on water supply in coastal regions and lead to major changes in groundwater recharge as well as the regional water balance as parts of the hydrosystem. These changes are threatening water security and, thereby, impede the fulfillment of the SDG 6 targets, esp. SDG targets 6.2., 6.4. and 6.6 of the UN 2030 Agenda for Sustainable Development. Thus, a modern water management demands innovative and profound methods and tools that comprehensively cover these complex changes. To address this challenge,  in the BMBF project "go-CAM" (Implementing strategic development goals in Coastal Aquifer Management) we took the methodological approach of developing new groundwater status indicators (e.g. chloride concentration in groundwater, position of saltwater/freshwater interface, freshwater volume) and corresponding target functions implemented in a new online-based management and evaluation tool called "CAM" (Coastal Aquifer Management). Both the physically based indicators as well as the target functions tackle economic as well as ecological issues. The groundwater status indicators are directly derived from the results of high-resolution, process-based (hydrological and hydrogeological) modeling of coastal hydrosystems. Due to their physical nature, the indicators are only applicable with appropriately designed climate and socio-economic scenarios for coastal water management if they are generated with models that also capture the system-relevant processes: Groundwater recharge, groundwater abstraction, discharge dynamics through drainage systems, sea level rise and groundwater discharge to the sea and saltwater intrusion.</p><p>The CAM platform is a tool that provides a way to make the results of the complex and extensive numerical modeling usable for a wider community and thus allow for a more efficient result exploitation. Building on the indicators and the selection of target functions and weighting factors the CAM tool uses Multi-Criteria Decision Analysis techniques (MCDA) to strengthen transparency and objectivity in decision-making processes and encourage communication between decision-makers in the water sector of coastal regions. In this way, the application of the CAM tool contributes to the establishment of an integrated water resources management and to derive and discuss future water management strategies as well as concrete measures.</p><p>Our methodological approach as well as the results are presented applied to a regional coastal groundwater study area in the northwestern part of Germany, the Sandelermöns region, which covers an area of about 1,000 km².</p>

An over-used ocean island coastal aquifer, Tenerife (Spain) – tracing inputs for improved resource management

<p>The island of Tenerife (Canary Islands, Spain) relies on basalt-hosted aquifers to provide 90% of water for agriculture and human consumption. The island is characterised by a low-permeability core, overlain by permeable materials which are cut by impermeable dykes. The effect is a compartmentalised aquifer, which is exploited sequentially as each “pocket” of water is exhausted. The island is home to ~1 million people (with an additional 5 million visiting tourists per year), and although rain/snowfall can be heavy in winter storms, it is unpredictable from year to year, and rapid surface water run off occurs due to the steep geography. While net recharge into the upper zones of the Tenerife aquifer have been quantified (around 2 months between intense rainfall and water table fluctuations), water must then follow a tortuous path to recharge lower zones and aquifer “pockets”. Water recharge to the coastal aquifers is also interrupted and extracted during its journey. Human and agricultural pressure is highest near the coast, and has led to intensive exploitation of existing wells and horizontal galleries. In response to the intensification of water extraction and slow recharge rates, marine intrusions into the coastal aquifers of Tenerife have occurred, traditionally recorded by rising chloride levels and resulting in well/gallery closures as well as increased pressure on other extraction sites. However, in a volcanic ocean island setting, natural processes can mimic the appearance of salinisation in a coastal aquifer. Management of aquifer resources require careful consideration of seawater incursions vs. volcanic degassing contributions vs. ocean island rainfall. Full hydrochemical breakdown of 43 coastal aquifer extraction sites reveal seawater intrusion is affecting the western coastal aquifer, with the agreement of multiple parameters. The strontium isotopic signature of well samples was also measured, because it is not subject to the biological or physical fractionation processes of other isotopic systems, thereby forming distinct reservoirs for groundwater (<sup>87</sup>Sr/<sup>86</sup>Sr of host rock), and seawater. <sup>87</sup>Sr/<sup>86</sup>Sr signatures suggest the northern coastal aquifers are also subject to seawater incursions. This parameter may be a more sensitive indicator than chlorides and conductivity markers for salinisation, especially in an ocean island environment where coastal aquifers are subject to intensive land use practices, seawater spray, and affected by diffuse volcanic degassing.</p>

Impact of Saline Ground water Pumping on density dependent Seawater circulation in Coastal aquifers

<p>Demand for more sustainable aquifer management solution has exacerbated in view of the seawater intrusion occurring in coastal aquifers, particularly in arid areas, where surface water is not aplenty. Feasibility studies showed saline ground water pumping from within saltwater wedge, aiding in mitigation of seawater intrusion and thus re-freshening the aquifer. Such pumping from nearshore aquifer mostly draws water from the sea. The impact is pronounced for higher pumping rates, where the interface would be lowered and toe position get shifted towards seaward side. This implies that, the change in fluid motion may reduce the outflow through seepage face, which in turn affect the circulation of seawater within the wedge. In the present study, a standard test aquifer was simulated with finite difference model, SEAWAT, to know the effect of change in hydraulic gradient due to pumping, on seawater circulation. Saltwater circulation rates were calculated as the ratio between the total inflow across the seaside boundary to terrestrial freshwater flow.  The result demonstrated the shape of interface to resume a depressed conical form establishing a dispersed interface near the surrounding of saline groundwater well. This localized dispersion observed deduce the presence of weak density gradients between two fluids, hence reducing convective overturn. Performance analysis were carried out to infer the interaction between density dependent seawater circulation and change in hydraulic gradient for different pumping rates. This interaction needs to be known in advance before designing saline water pumping rates, as, significant transport of nutrients and contaminants occur within the saltwater wedge.</p>