•Neglecting SW-GW feedback in groundwater flow modelling is highly likely to result in the simulation of overly deep (disconnected) water tables in shallow regional aquifer systems.•The consideration ...of two-way feedback is of larger importance when simulating low-flow periods compared to high-flow periods.•The inclusion of SW-GW feedback may reduce the potential of water table elevation observations to constrain hydraulic conductivity for model calibration.
Groundwater flow models are increasingly considered for the regional scale simulation of hydraulic heads and water table elevation. In the most complete configuration, models explicitly simulate two-way interactions between surface water (SW) and groundwater (GW) to reproduce and forecast both SW and GW water levels. In most regional scale groundwater models, however, SW-GW interactions are represented by simplified boundary conditions that only allow one-way interaction from SW to GW, neglecting most of the dynamic exchange fluxes between SW and GW. To evaluate the potential consequences of such simplifications on the simulation of regional GW levels, we compare two models on a 36,900 km2 regional aquifer system in Southern Quebec. One model explicitly simulates both SW and GW flow with two-way SW-GW feedback and the other model only simulates GW flow with a surface boundary flux to represent a one-way interaction with the land surface. Both models are developed with the same numerical code to ensure that the only differences are the representation of SW water flow and SW-GW feedback. The one-way model simulates overall deeper water tables because it removes all exfiltrated groundwater from the system once it exits the subsurface, therefore not allowing exfiltrating groundwater to re-infiltrate. This effect is most pronounced in areas where the water table is close to the surface and for low-flow periods. The inclusion of two-way feedback also reduces the sensitivity of simulated GW levels to the magnitude of the hydraulic conductivity. This result highlights the need for additional data on other system states to improve the calibration of regional scale models that explicitly simulate two-way SW-GW interactions.
•Anthropogenic effect over river-aquifer interaction pattern is investigated.•Three critical interaction zones are identified from upstream to downstream.•A framework is proposed to assess ...interaction exchange flux in alluvial rivers.
The easy accessibility of groundwater in the alluvial plains of the Kosi river basin has considerably altered the crop calendar and farmers’ irrigation response, especially in the dry years after 2004. The present study attempts to develop a framework for analyzing the spatio-temporal variation in the groundwater recharge/ extraction pattern as well as river and aquifer flux exchange due to increasing anthropogenic activities in the basin. The influence of anthropogenic activities over groundwater recharge/extraction statistics has been discussed in Laveti et al. (2021). The estimated groundwater recharge (Laveti et al., 2021) along with aquifer characteristics (hydraulic conductivity, porosity, and specific storage), and riverbed conductance were used as inputs to the groundwater flow transient model in the study. The model observed, an increasing groundwater dependency for agricultural activities, results in a continuous increase of flux from the river to the aquifer. Between 1997 and 2010, the river to aquifer flux increased by almost 1% of the average river discharge. This increase in river to aquifer flux exchange was evident, especially during the dry periods after 2004, which coincided with the government’s Million Shallow Tube Well Programme (MSTP) in the basin. The increasing trend of the river to aquifer flux transfer and the decreasing trend of the aquifer to river flux transfer observed in the Kosi basin can have disturbing long-term effects in terms of reduced river flow and river stage. Therefore, the concerned authorities and the stakeholders must take immediate notice of the observations.
•Climate change impact on groundwater levels (GWL) varies spatially.•The climate change impact response reflects the dominating hydrological processes.•An ensemble of climate and land surface models ...shows the uncertainty of future GWL.•Climate models are the main source of uncertainty for predicting future GWL.•Uncertainty from the land surface models increases for high GWL and near the river.
This paper presents the first study assessing the climate change impact on groundwater levels of the Zagreb alluvial aquifer in Croatia by coupling climate projections under RCP8.5 for the period 2040–2070 with local scale groundwater flow modelling. As a novelty in groundwater modelling of climate change impacts, this study utilizes an ensemble of five climate models and two land surface models for providing projections of relevant boundary conditions to the groundwater model. The groundwater model is used for predicting climate driven changes in groundwater levels in the aquifer system influenced by both changes in local groundwater recharge and changes in river-flow. Both boundary conditions are obtained from the land surface models. In addition, the uncertainty contributions to groundwater levels from both climate models and land surface models were quantified using variance decomposition. The results revealed that the spatial pattern of changes in groundwater levels can be related to different processes influencing groundwater dynamics. In areas dominated by a strong groundwater-surface water interaction, close to the Sava river, the multi-model ensemble mean change in groundwater levels is negligible for low and average water levels. However, for high water levels, an increase was identified. In contrast, a decline in groundwater levels prevails in all areas where aquifer recharge is largely driven by rainfall infiltration. For the variance decomposition analysis, climate models were identified as the main source of uncertainty for groundwater levels. However, the uncertainty contribution of the choice of land surface model to the impact simulations was found to be more important in the area affected by a strong groundwater–surface water interaction and for periods of high groundwater levels. Also, specific local issues related to low and high groundwater levels that are associated with extreme hydrological regimes were found to exacerbate under climate projections.
Non‐perennial streams play a crucial role in ecological communities and the hydrological cycle. However, the key parameters and processes involved in stream intermittency remain poorly understood. ...While climatic conditions, geology and land use are well identified, the assessment and modelling of groundwater controls on streamflow intermittence remain a challenge. In this study, we explore new opportunities to calibrate process‐based 3D groundwater flow models designed to simulate hydrographic network dynamics in groundwater‐fed headwaters. Streamflow measurements and stream network maps are considered together to constrain the effective hydraulic properties of the aquifer in hydrogeological models. The simulations were then validated using visual observations of water presence/absence, provided by a national monitoring network in France (ONDE). We tested the methodology on two pilot unconfined shallow crystalline aquifer catchments, the Canut and Nançon catchments (Brittany, France). We found that both streamflow and stream network expansion/contraction dynamics are required to calibrate models that simultaneously estimate hydraulic conductivity K$$ K $$ and porosity Φ$$ \varPhi $$ with low uncertainties. The calibration allowed good prediction of stream intermittency, both in terms of flow and spatial extent. For the two catchments studied, Canut and Nançon, the hydraulic conductivity is close reaching 1.5 × 10−5 m/s and 4.5 × 10−5 m/s, respectively. However, they differ more in their storage capacity, with porosity estimated at 0.1% and 2.2%, respectively. Lower storage capacity leads to higher groundwater level fluctuations, shorter aquifer response times, an increase in the proportion of intermittent streams and a reduction in perennial flow. This new modelling framework for predicting headwater streamflow intermittence can be deployed to improve our understanding of groundwater controls in different geomorphological, geological and climatic contexts. It will benefit from advances in remote sensing and crowdsourcing approaches that generate new observational data products with high spatial and temporal resolution.
This study proposes a new methodology for calibrating headwater groundwater flow models by combining streamflow time series and maps of perennial and intermittent stream networks. The methodology is tested in two catchments where we evaluate strong contrasts in hydraulic conductivity and porosity to explain differences in stream intermittency dynamics. Our results provide a valuable framework for modelling poorly gauged basins and better understanding the groundwater controls on stream intermittency, with potential extensions using remote sensing and crowdsourced data.
Managed Aquifer Recharge (MAR) has emerged as a multi-facet, sustainable and effective technique to replenish dwindling groundwater resources. Suitable site selection is an important step in the ...design phase of MAR process. Conventional methods of site suitability studies using GIS and Multi Criteria Decision Analysis (MCDA) does not address the aquifer’s response to MAR, while limited modelling-based studies have considered the effect of surface hydraulic factors. In this paper, a fresh approach is presented, that utilises decision model, K-mean clustering technique and numerical model to identify optimal sites for MAR interventions. The methodology was applied in a semi-arid region of Lower Betwa River Basin (LBRB), India. Four different parameter combinations were employed that incorporated the impact of surface and subsurface parameters. Multiple model runs were executed using MODFLOW–NWT to assess the groundwater head response to the infiltrated volume of water. The results indicated that under the least head change category (< 0.7 m), the north and south–east regions of the LBRB were the most appropriate sites. The coalition of geomorphology and drainage density along with aquifer properties such as hydraulic conductivity, specific yield and aquifer thickness were found to be the best suited combination for site selection in LBRB, with maximum spatial coverage (16%) under it. It was observed that the choice of parameter combinations affected the range of groundwater head variations and depended upon the site-specific criteria of accepted head change ranges for determining the best suitable parameter combinations for MAR site selection.
Aquifer recharge is one of the most important hydrologic parameters for understanding available groundwater volumes and making sustainable the use of natural water by minimizing groundwater mining. ...In this framework, we reviewed and evaluated the efficacy of multiple methods to determine recharge in a flood basalt terrain that is restrictive to infiltration and percolation. In the South Fork of the Columbia River Plateau, recent research involving hydrologic tracers and groundwater modeling has revealed a snowmelt-dominated system. Here, recharge is occurring along the intersection of mountain-front alluvial systems and the extensive Miocene flood basalt layers that form a fractured basalt and interbedded sediment aquifer system. The most recent groundwater flow model of the basin was based on a large physio-chemical dataset acquired in laterally and vertically distinctive locations that refined the understanding of the intersection of the margin alluvium and the spatially variable basalt flows that filled the basin. Modelled effective recharge of 25 and 105 mm/year appears appropriate for the basin’s plain and the mountain front, respectively. These values refine previous efforts on quantifying aquifer recharge based on Darcy’s law, one-dimensional infiltration, zero-flux plane, chloride, storage, and mass-balance methods. Overall, the combination of isotopic hydrochemical data acquired in three dimensions and flow modelling efforts were needed to simultaneously determine groundwater dynamics, recharge pathways, and appropriate model parameter values in a primarily basalt terrain. This holistic approach to understanding recharge has assisted in conceptualizing the aquifer for resource managers that have struggled to understand aquifer dynamics and sustainable withdrawals.
Mabou Harbour located in Cape Breton Island, Nova Scotia, Canada, is representative of the many natural harbours throughout the Maritime region of Canada as the surrounding landscape is overlain by ...glacial deposits, predominantly composed of glacial till.
Understanding the pathways facilitating groundwater flow and associated solute transport to the ocean is key for developing conceptual hydrogeologic models for coastal watersheds and for informing coastal zone management. Most local-scale field and modelling submarine groundwater discharge (SGD) studies have been conducted in high-permeability formations given the likely importance of SGD in these coastal settings. This study investigates direct (SGD) and indirect (seaward stream baseflow) groundwater discharge from a till dominated coastal aquifer using a combination of field measurements (river flow and baseflow separation, seepage meter measurements, and water temperature analysis) and a calibrated 3D numerical groundwater flow model.
Results show that seaward stream baseflow greatly exceeds direct SGD to the ocean on the scale of the full harbour watershed (96.1% vs. 3.9 of total groundwater discharge). Particle tracking shows that the vast majority of SGD originates in the subcatchment immediately surrounding the harbour with limited intermediate or regional flow. The shorter flow paths and residence times for direct SGD results in less opportunity for natural attenuation processes and may have implications for groundwater-borne contamination to this harbour.
•Field data and a model are used to assess coastal groundwater discharge pathways.•Groundwater-derived baseflow contributes 96.1% of coastal groundwater discharge.•SGD contributes only 3.9% of groundwater discharge to the coast.•SGD rates along this till-dominated coast are much lower than in most past studies.•SGD is delivered via local groundwater flow pathways with short residence times.
Northern Finland.
This study examined long-term (decade-scale) hydrological and ecological consequences of dam construction and subsequent river regulation on the environmentally protected ...Viiankiaapa mire. Pre-regulation floods affected the hydrology of the riverbanks and the Viiankiaapa mire, which contain habitats of flood-dependent or groundwater-influenced ecosystems. Groundwater discharge and flow patterns and pre-regulation flood coverage were simulated to investigate the impact of river regulation on the mire area.
The flood models indicate that regular flooding covered the westernmost part of the mire before the regulation. Groundwater modelling suggests that the regulation has raised the locations of springs in the river shore, reduced the hydraulic gradient towards the river, raised the groundwater table in the river banks and the western part of the Viiankiaapa mire, and increased groundwater discharge in the mire. The groundwater flow models and the stable isotopic composition of water indicate that the constructed dam changed the groundwater flow directions close to dam. The ecological effects of regulation were mixed: the studied flood-dependent plant species declined due to the reduction in floods after regulation. Conversely, the occurrence of Hamatocaulis vernicosus and Hamatocaulis lapponicus appears to be related to the high water table and groundwater discharge areas in the mire, suggesting suitable habitat for these species may have expanded after the regulation.
•River regulation has affected the mire in the mining development site.•Both groundwater flow modelling and flood modelling was considered.•The regulation has reduced the flood coverage and hydraulic gradient.•The regulation raised the water table in the western part of the mire.•Flooding has affected the flood and groundwater influenced habitats.
Groundwater models are often used to predict the future behaviour of groundwater systems. These models may vary in complexity from simplified system conceptualizations to more intricate versions. It ...has been recently suggested that uncertainties in model predictions are largely dominated by uncertainties arising from the definition of alternative conceptual models. Different external factors such as climatic conditions or groundwater abstraction policies, on the other hand, may also play an important role.
Rojas et al. (2008) proposed a multimodel approach to account for predictive uncertainty arising from forcing data (inputs), parameters and alternative conceptualizations. In this work we extend upon this approach to include uncertainties arising from the definition of alternative future scenarios and we apply the extended methodology to a real aquifer system underlying the Walenbos Nature Reserve area in Belgium. Three alternative conceptual models comprising different levels of geological knowledge are considered. Additionally, three recharge settings (scenarios) are proposed to evaluate recharge uncertainties. A joint estimation of the predictive uncertainty including parameter, conceptual model and scenario uncertainties is estimated for groundwater budget terms. Finally, results obtained using the improved approach are compared with the results obtained from methodologies that include a calibration step and which use a model selection criterion to discriminate between alternative conceptualizations. Results showed that conceptual model and scenario uncertainties significantly contribute to the predictive variance for some budget terms. Besides, conceptual model uncertainties played an important role even for the case when a model was preferred over the others. Predictive distributions showed to be considerably different in shape, central moment and spread among alternative conceptualizations and scenarios analysed. This reaffirms the idea that relying on a single conceptual model driven by a particular scenario, will likely produce bias and under-dispersive estimations of the predictive uncertainty. Multimodel methodologies based on the use of model selection criteria produced ambiguous results. In the frame of a multimodel approach, these inconsistencies are critical and can not be neglected. These results strongly advocate the idea of addressing conceptual model uncertainty in groundwater modelling practice. Additionally, considering alternative future recharge uncertainties will permit to obtain more realistic and, possibly, more reliable estimations of the predictive uncertainty.
In Belgium, IWVA uses managed aquifer recharge (MAR) to recharge the aquifer with treated wastewater generated from the communities to sustain the potable water supply on the Belgian coast. This MAR ...facility is faced with a challenge of reduced infiltration rates during the winter season when pond water temperatures near 4°C. This study involves the identification of the predominant factor influencing the rate of infiltration through the pond bed. Several factors, including pumping rates, natural recharge, tidal influences of the North Sea and pond‐water temperature, were identified as potential causes for variation of the recharge rate. Correlation statistics and linear regression analysis were used to determine the sensitivity of the infiltration rate to the aforementioned factors. Two groundwater flow models were developed in visual MODFLOW to simulate the water movement under the pond bed and to obtain the differences in flux to track the effects of variation of hydraulic conductivity during the two seasons. A 32% reduction in vertical hydraulic gradient in the top portion of the aquifer was observed in winter, causing the recharge rates to fluctuate. Results showed that water temperature caused a 30% increase in hydraulic conductivity in summer as compared with winter and has the maximum impact on infiltration rate. Cyclic variations in water viscosity, occurring because of seasonal temperature changes, influence the saturated hydraulic conductivity of the pond bed. Results from the models confirm the impact on infiltration rate by temperature‐influenced hydraulic conductivity.
Temperature and infiltration rates have been found to be very well correlated when it comes to MAR. This study in St‐André, Belgium revealed that temperature variations could cause a massive 30% increase in hydraulic conductivity in summer than that in the winter. Also, 32% reduction in vertical hydraulic gradient was observed in the top portion of the aquifer, which directly influenced the recharge rates in the MAR facility.
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