Water

Research

28 pages, 4642 KiB

Open AccessFeature PaperArticle

Modelling Projected Changes in Soil Water Budget in Coastal Kenya under Different Long-Term Climate Change Scenarios

by Cornelius Okello, Nicolas Greggio, Beatrice Maria Sole Giambastiani, Nina Wambiji, Julius Nzeve and Marco Antonellini

Water 2020, 12(9), 2455; https://doi.org/10.3390/w12092455 - 1 Sep 2020

Cited by 2 | Viewed by 3821

Abstract

The possible impacts that climate change will have on soil water budget and specifically on deep percolation, runoff and soil water content have been investigated using HYDRUS, a methodology based on numerical modelling simulations of vertical water movement in a homogenous soil column [...] Read more.

The possible impacts that climate change will have on soil water budget and specifically on deep percolation, runoff and soil water content have been investigated using HYDRUS, a methodology based on numerical modelling simulations of vertical water movement in a homogenous soil column on a flat surface. This study was carried out on four typical soil types occurring on the Kenyan coast and the adjacent hinterlands of up to an elevation of 200 m above sea level (m a.s.l.) covered by five weather stations (two dry and three wet stations). Results show that deep percolation and runoff are expected to be higher in 2100 for both Relative Concentration Pathways (RCPs) 2.6 and 8.5 scenarios than they were for the reference period (1986–2005). The average deep percolation is expected to increase by 14% for RCP 2.6 and 10% for the RCP 8.5, while the average runoff is expected to increase by 188% and 284% for the same scenarios. Soil water content is expected to either increase marginally or reduce depend in the same scenarios. The average soil water content is also expected to increase by 1% in the RCP 2.6 scenario and to decrease by 2% in the RCP 8.5 scenario. Increase in deep percolation through clay soil is expected to be the largest (29% in both scenarios), while sandy and sandy clay soil are expected to be the least influenced with an average increase of only 2%. Climate change is expected to impact runoff mostly in sandy soils, whereas the least affected would be clay loam soils. These results further support the assertion that the change in climate is expected to impact the recharge of aquifers by triggering an increase in infiltration under both scenarios. Full article

(This article belongs to the Special Issue Advances in Groundwater and Surface Water Monitoring and Management)

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23 pages, 4903 KiB

Open AccessArticle

The Role of Environmental Background Processes in Determining Groundwater Level Variability—An Investigation of a Record Flood Event Using Dynamic Factor Analysis

by Balázs Trásy, Norbert Magyar, Tímea Havril, József Kovács and Tamás Garamhegyi

Water 2020, 12(9), 2336; https://doi.org/10.3390/w12092336 - 20 Aug 2020

Cited by 5 | Viewed by 2195

Abstract

Since groundwater is a major source of water for drinking and for industrial and irrigation uses, the identification of the environmental processes determining groundwater level fluctuation is potentially a matter of great consequence, especially in light of the fact that the frequency of [...] Read more.

Since groundwater is a major source of water for drinking and for industrial and irrigation uses, the identification of the environmental processes determining groundwater level fluctuation is potentially a matter of great consequence, especially in light of the fact that the frequency of extreme climate events may be expected to increase, causing changes in groundwater recharge systems. In the recent study, data measured at a frequency of one hour were collected from the Szigetköz, an inland delta of the Danube. These were then used to determine the presence, or not, and magnitude of any hidden environmental background factors that may be causing groundwater level fluctuations. Through the application of dynamic factor analysis, it was revealed that changes in groundwater level are mainly determined by (i) the water level of neighboring rivers and (ii) evapotranspiration. The intensity of these factors may also be estimated spatially. If the background factors determined by dynamic factor analysis do indeed figure in the linear model as variables, then the time series of groundwater levels can be said to have been accurately estimated with the use of linear regression. The accuracy of the estimate is indicated by the fact that adjusted coefficient of determination exceeds 0.9 in 80% of the wells. The results, via an enhanced understanding of the reasons for changes in the fluctuation of groundwater, could assist in the development of sustainable water management and irrigation strategies and the preparation for varying potential climate change scenarios. Full article

(This article belongs to the Special Issue Advances in Groundwater and Surface Water Monitoring and Management)

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20 pages, 4541 KiB

Open AccessArticle

Extraction Method of Baseflow Recession Segments Based on Second-Order Derivative of Streamflow and Comparison with Four Conventional Methods

by Weifei Yang, Changlai Xiao and Xiujuan Liang

Water 2020, 12(7), 1953; https://doi.org/10.3390/w12071953 - 9 Jul 2020

Cited by 8 | Viewed by 3556

Abstract

Baseflow recession analysis is widely used in hydrological research, water resource planning and management, and watershed hydrogeological research. The first step of baseflow recession analysis is to extract the baseflow recession segments from the hydrograph. Different extraction results lead to different analysis results. [...] Read more.

Baseflow recession analysis is widely used in hydrological research, water resource planning and management, and watershed hydrogeological research. The first step of baseflow recession analysis is to extract the baseflow recession segments from the hydrograph. Different extraction results lead to different analysis results. At present, the four major recession segment extraction methods applied by hydrologists are mostly based on experience, and there is no clear theoretical basis. Therefore, this study derives a second-order derivation (Sec-D) recession segment extraction method based on the power law relationship between storage and discharge. Moreover, by applying the Sec-D method and the four conventional extraction methods to four hydrological stations in the Tao’er River basin in northeastern China, the differences in the recession segment extraction, determination of basin-wide hydrogeological parameters, and groundwater balance estimation are compared. The results demonstrate that, contrary to the four conventional methods, the Sec-D method can effectively eliminate the early recession stage affected by the surface runoff or rainfall and some streamflow data with more than 1% non-sequential error. The hydraulic conductivity of the four basins estimated by the Sec-D method is between 2.3 × 10⁻⁵–4.9 × 10⁻⁵ m/s, and the aquifer thickness is between 131.2 and 202.5 m. However, the four conventional extraction methods may underestimate (by about 2.5 times) the basin-wide hydraulic conductivity and overestimate (by about 3 times) the aquifer thickness. The groundwater balance elements calculated by the Sec-D method and the four conventional methods present similar intra-annual fluctuation characteristics; the correlation coefficients of daily evapotranspiration calculated by the five methods ranged from 0.7 to 0.95, and those of daily effective groundwater recharge ranged from 0.95 to 0.99. The use of the Sec-D method in baseflow recession analyses is significant for future studies and can be combined with conventional methods. Full article

(This article belongs to the Special Issue Advances in Groundwater and Surface Water Monitoring and Management)

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26 pages, 7036 KiB

Open AccessFeature PaperArticle

Assessment of the Main Geochemical Processes Affecting Surface Water and Groundwater in a Low-Lying Coastal Area: Implications for Water Management

by Nicolas Greggio, Beatrice M. S. Giambastiani, Pauline Mollema, Mario Laghi, Donato Capo, Giovanni Gabbianelli, Marco Antonellini and Enrico Dinelli

Water 2020, 12(6), 1720; https://doi.org/10.3390/w12061720 - 16 Jun 2020

Cited by 13 | Viewed by 4286

Abstract

Hydrogeochemical analyses were carried out to identify geochemical processes occurring in the low-lying coastal aquifer of Ravenna, North Adriatic Sea (Italy). The area is characterized by a complex coexistence of several environments: coastal dunes, paleodunes, pine forests, freshwater wetlands, rivers, brackish lagoons, gravel [...] Read more.

Hydrogeochemical analyses were carried out to identify geochemical processes occurring in the low-lying coastal aquifer of Ravenna, North Adriatic Sea (Italy). The area is characterized by a complex coexistence of several environments: coastal dunes, paleodunes, pine forests, freshwater wetlands, rivers, brackish lagoons, gravel pit lakes, reclaimed lands, agricultural fields and industrial areas. Water quality is of primary importance for the sustainability of these, areas and a full understanding of geochemical processing is fundamental for their management. A total of 104 water samples was collected from groundwater wells and surface water bodies, and analyzed for the major and trace elements (TEs). Field measurements of chemical-physical parameters were carried out by a multiparameter device XS PCD650; major elements were analyzed following the Italian National Environmental Agency standards (APAT-IRSA 2003), while TEs were analyzed by ICP-AES/ICP-MS. The major findings include: organic matter degradation in salinized and anoxic conditions; TEs concentrations related to water–sediment interactions, i.e., adsorption, ion exchange, redox reactions, mineral dissolution and precipitation; anthropogenic contamination from pesticides and fertilizers use; pollution from industrial district; TEs enrichments and depletion due to groundwater salinization and water management practices; comparison of TEs concentrations with respect to national and international thresholds. The findings can provide water managers and local authorities with a comprehensive framework of the coastal water hydrochemistry, allowing a better understanding of the effects of current management practices and the design of mitigation measures to reduce water resource deterioration in the studied coastal area. Full article

(This article belongs to the Special Issue Advances in Groundwater and Surface Water Monitoring and Management)

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15 pages, 13317 KiB

Open AccessArticle

Sentinel-2 Application to the Surface Characterization of Small Water Bodies in Wetlands

by Jesús Pena-Regueiro, Maria-Teresa Sebastiá-Frasquet, Javier Estornell and Jesús Antonio Aguilar-Maldonado

Water 2020, 12(5), 1487; https://doi.org/10.3390/w12051487 - 22 May 2020

Cited by 26 | Viewed by 5268

Abstract

Developing indicators to monitor environmental change in wetlands with the aid of Earth Observation Systems can help to obtain spatial data that is not feasible with in situ measures (e.g., flooding patterns). In this study, we aim to test Sentinel-2A/B images suitability for [...] Read more.

Developing indicators to monitor environmental change in wetlands with the aid of Earth Observation Systems can help to obtain spatial data that is not feasible with in situ measures (e.g., flooding patterns). In this study, we aim to test Sentinel-2A/B images suitability for detecting small water bodies in wetlands characterized by high diversity of temporal and spatial flooding patterns using previously published indices. For this purpose, we used medium spatial resolution Sentinel-2A/B images of four representative coastal wetlands in the Valencia Region (East Spain, Mediterranean Sea), and on three different dates. To validate the results, 60 points (30 in water areas and 30 in land areas) were distributed randomly within a 20 m buffer around the border of each digitized water polygon for each date and wetland (600 in total). These polygons were mapped using as a base map orthophotos of high spatial resolution. In our study, the best performing index was the NDWI. Overall accuracy and Kappa index results were optimal for −0.30 threshold in all the studied wetlands and dates. The consistency in the results is key to provide a methodology to characterize water bodies in wetlands as generalizable as possible. Most studies developed in wetlands have focused on calculating global gain or loss of wetland area. However, inside of wetlands which hold protection figures, the main threat is not necessarily land use change, but rather water management strategies. Applying Sentinel-2A/B images to calculate the NDWI index and monitor flooded area changes will be key to analyse the consequence of these management actions. Full article

(This article belongs to the Special Issue Advances in Groundwater and Surface Water Monitoring and Management)

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17 pages, 3410 KiB

Open AccessFeature PaperArticle

Low-Cost, Open Source Wireless Sensor Network for Real-Time, Scalable Groundwater Monitoring

by Andrew J. Calderwood, Richard A. Pauloo, Alysa M. Yoder and Graham E. Fogg

Water 2020, 12(4), 1066; https://doi.org/10.3390/w12041066 - 9 Apr 2020

Cited by 23 | Viewed by 8033

Abstract

Population growth, climate uncertainties, and unsustainable groundwater pumping challenge aquifer sustainability worldwide. Efficient and data-driven groundwater supply management is a necessity to maintain essential water-dependent functions. Currently, managers lack the cost-effective, scalable, and reliable groundwater monitoring systems needed to collect vital groundwater data. [...] Read more.

Population growth, climate uncertainties, and unsustainable groundwater pumping challenge aquifer sustainability worldwide. Efficient and data-driven groundwater supply management is a necessity to maintain essential water-dependent functions. Currently, managers lack the cost-effective, scalable, and reliable groundwater monitoring systems needed to collect vital groundwater data. Existing automated groundwater monitoring systems tend to be cost-prohibitive, and manual methods lack the spatial or temporal resolution to sufficiently meet critical water modeling, management, and policy objectives. In this study, we developed a fully automated, open source, low cost wireless sensor network (LCSN) for real-time groundwater data acquisition, processing, and visualization in the South American Subbasin Groundwater Observatory (GWO), located in California, USA. We demonstrate the steps taken to create the GWO, including field, hardware, software, and data pipeline components so that it may be easily reproduced in new areas. We find that the GWO is comparable in cost to manual measurements at a weekly measurement frequency, and costs between three and four times less than comparable commercially available telemetry and dashboard systems, largely due to the use of free open source software to acquire, clean, store, and visualize data. The open source-powered GWO thus lowers the financial and technical barrier of entry for real-time groundwater monitoring, creating the potential for more informed water management worldwide, particularly in regions whose managers are restricted by the high capital costs of commercial monitoring systems. Full article

(This article belongs to the Special Issue Advances in Groundwater and Surface Water Monitoring and Management)

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14 pages, 3741 KiB

Open AccessFeature PaperArticle

Monitoring and Modelling Interactions between the Montagna dei Fiori Aquifer and the Castellano Stream (Central Apennines, Italy)

by Alberto Tazioli, Nicolò Colombani, Stefano Palpacelli, Micòl Mastrocicco and Torquato Nanni

Water 2020, 12(4), 973; https://doi.org/10.3390/w12040973 - 30 Mar 2020

Cited by 7 | Viewed by 2975

Abstract

Groundwater is the most used water resource around the world, but due to population growth and climate change the alluvial lowland aquifers are often polluted and over-exploited. Thus, more and more frequently water managers need to shift their attention to mountain regions to [...] Read more.

Groundwater is the most used water resource around the world, but due to population growth and climate change the alluvial lowland aquifers are often polluted and over-exploited. Thus, more and more frequently water managers need to shift their attention to mountain regions to identify groundwater resources for drinking purposes. This study presents a monitoring and modelling approach that allowed to quantify the inflow from the “Montagna dei Fiori” fractured aquifer to the Castellano stream. Continuous monitoring of flow discharge and temperature during an entire hydrological year (2018–2019) at two monitoring stations along the stream allowed to discriminate between the baseflow (on average, 0.891 m³/s) and the run-off (on average, 0.148 m³/s) components. A hydrogeological basin-wide numerical flow model (using MODFLOW-2005) was set up using information from hydrogeological and geomechanical surveys. The model was calibrated using the daily baseflow observations made in the Castellano stream (R² = 0.75). The calibrated model allowed to quantify groundwater/surface water interactions. After an automated sensitivity analysis (using MODFLOW-2000), the recharge was found to be the most uncertain parameter, followed by the hydraulic conductivity zonation. This methodology could be applied in other mountain regions where groundwater monitoring networks are usually lacking to improve water resources management. Full article

(This article belongs to the Special Issue Advances in Groundwater and Surface Water Monitoring and Management)

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16 pages, 5375 KiB

Open AccessArticle

Hydraulic Conductivity Estimation Using Low-Flow Purging Data Elaboration in Contaminated Sites

by Francesco Maria De Filippi, Silvia Iacurto, Flavia Ferranti and Giuseppe Sappa

Water 2020, 12(3), 898; https://doi.org/10.3390/w12030898 - 22 Mar 2020

Cited by 8 | Viewed by 5896

Abstract

Hydrogeological characterization is required when investigating contaminated sites, and hydraulic conductivity is an important parameter that needs to be estimated. Before groundwater sampling, well water level values are measured during low-flow purging to check the correct driving of the activity. However, these data [...] Read more.

Hydrogeological characterization is required when investigating contaminated sites, and hydraulic conductivity is an important parameter that needs to be estimated. Before groundwater sampling, well water level values are measured during low-flow purging to check the correct driving of the activity. However, these data are generally considered only as an indicator of an adequate well purging. In this paper, water levels and purging flow rates were considered to estimate hydraulic conductivity values in an alluvial aquifer, and the obtained results were compared with traditional hydraulic conductivity test results carried on in the same area. To test the applicability of this method, data coming from 59 wells located in the alluvial aquifer of Malagrotta waste disposal site, a large area of 160 ha near Rome, were analyzed and processed. Hydraulic conductivity values were estimated by applying the Dupuit’s hypothesis for steady-state radial flow in an unconfined aquifer, as these are the hydraulic conditions in pumping wells for remediation purposes. This study aims to show that low-flow purging procedures in monitoring wells—carried out before sampling for groundwater characterization—represent an easy and inexpensive method for soil hydraulic conductivity estimation with good feasibility, if correctly carried on. Full article

(This article belongs to the Special Issue Advances in Groundwater and Surface Water Monitoring and Management)

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22 pages, 4831 KiB

Open AccessArticle

E-DATA: A Comprehensive Field Campaign to Investigate Evaporation Enhanced by Advection in the Hyper-Arid Altiplano

by Francisco Suárez, Felipe Lobos, Alberto de la Fuente, Jordi Vilà-Guerau de Arellano, Ana Prieto, Carolina Meruane and Oscar Hartogensis

Water 2020, 12(3), 745; https://doi.org/10.3390/w12030745 - 8 Mar 2020

Cited by 17 | Viewed by 4171

Abstract

In the endorheic basins of the Altiplano, water is crucial for sustaining unique ecological habitats. Here, the wetlands act as highly localized evaporative environments, and little is known about the processes that control evaporation. Understanding evaporation in the Altiplano is challenging because these [...] Read more.

In the endorheic basins of the Altiplano, water is crucial for sustaining unique ecological habitats. Here, the wetlands act as highly localized evaporative environments, and little is known about the processes that control evaporation. Understanding evaporation in the Altiplano is challenging because these environments are immersed in a complex topography surrounded by desert and are affected by atmospheric circulations at various spatial scales. Also, these environments may be subject to evaporation enhancement events as the result of dry air advection. To better characterize evaporation processes in the Altiplano, the novel Evaporation caused by Dry Air Transport over the Atacama Desert (E-DATA) field campaign was designed and tested at the Salar del Huasco, Chile. The E-DATA combines surface and airborne measurements to understand the evaporation dynamics over heterogeneous surfaces, with the main emphasis on the open water evaporation. The weather and research forecasting model was used for planning the instruments installation strategy to understand how large-scale air flow affects evaporation. Instrumentation deployed included: meteorological stations, eddy covariance systems, scintillometers, radiosondes and an unmanned aerial vehicle, and fiber-optic distributed temperature sensing. Additional water quality and CO₂ fluxes measurements were carried out to identify the link between meteorological conditions and the biochemical dynamics of Salar del Huasco. Our first results show that, in the study site, evaporation is driven by processes occurring at multiple spatial and temporal scales and that, even in the case of available water and energy, evaporation is triggered by mechanical turbulence induced by wind. Full article

(This article belongs to the Special Issue Advances in Groundwater and Surface Water Monitoring and Management)

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19 pages, 3945 KiB

Open AccessArticle

Assessment of Seasonal Changes in Water Chemistry of the Ridracoli Water Reservoir (Italy): Implications for Water Management

by Simone Toller, Beatrice M. S. Giambastiani, Nicolas Greggio, Marco Antonellini, Ivo Vasumini and Enrico Dinelli

Water 2020, 12(2), 581; https://doi.org/10.3390/w12020581 - 20 Feb 2020

Cited by 9 | Viewed by 4588

Abstract

The Ridracoli artificial basin is the main water reservoir of the Emilia-Romagna region (Northeast Italy). The reservoir was made by construction of a dam on the Bidente River in 1982. It is used as the main drinking water supply of the region and [...] Read more.

The Ridracoli artificial basin is the main water reservoir of the Emilia-Romagna region (Northeast Italy). The reservoir was made by construction of a dam on the Bidente River in 1982. It is used as the main drinking water supply of the region and for hydropower production. The physical and chemical parameterseters (temperature, pH, electrical conductivity, and dissolved oxygen) of shallow water are continuously monitored whereas vertical depth profiles of water chemical data (major anions and cations, as well as heavy metals) are available on a bimonthly base. The dataset used in this research is related to the years 2015 and 2016. Data show that the reservoir is affected by an alternation of water stratification and mixing processes due to seasonal change in water temperature, density, and the reservoir water level. In late summer and winter months, the water column is stratified with anoxic conditions at the bottom. During the spring, on the other hand, when storage is at its maximum, water recirculation and mixing occur. The reservoir is characterized by a dynamic system in which precipitation, dissolution, and adsorption processes at the bottom affect water quality along the reservoir depth column. The temperature stratification and anoxic conditions at the reservoir bottom influence the concentration and mobility of some heavy metals (i.e., Fe and Mn) and, consequently, the quality of water that reaches the treatment and purification plant. This study is relevant for water resource management of the reservoir. Assessing the seasonal changes in water quality along the reservoir water column depth is fundamental to plan water treatment operations and optimize their costs. The reservoir assessment allows one to identify countermeasures to avoid or overcome the high concentrations of heavy metals and the stratification problem (i.e., artificial mixing of the water column, new water intakes at different depths operating at different times of the year, blowers, etc.). Full article

(This article belongs to the Special Issue Advances in Groundwater and Surface Water Monitoring and Management)

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16 pages, 7625 KiB

Open AccessArticle

Analysis of Seepage in a Laboratory Scaled Model Using Passive Optical Fiber Distributed Temperature Sensor

by Yaser Ghafoori, Matej Maček, Andrej Vidmar, Jaromír Říha and Andrej Kryžanowski

Water 2020, 12(2), 367; https://doi.org/10.3390/w12020367 - 29 Jan 2020

Cited by 25 | Viewed by 5421

Abstract

Seepage is the key factor in the safety of dikes and earth-fill dams. It is crucial to identify and localize the seepage excesses at the early stages before it initiates the internal erosion process in the structure. A proper seepage monitoring system should [...] Read more.

Seepage is the key factor in the safety of dikes and earth-fill dams. It is crucial to identify and localize the seepage excesses at the early stages before it initiates the internal erosion process in the structure. A proper seepage monitoring system should ensure a continuous and wide area seepage measurement. Here, continuous monitoring of seepage at the laboratory-scale is achieved by a passive optical fiber Distributed Temperature Sensing (DTS) system. An experimental model was designed which consists of initially unsaturated sand model, water supply, seepage outflow, optical fiber DTS system, and water and air temperature measurement. Initially, the sand temperature was higher than the temperature of the seepage water. An optical fiber DTS system was employed with a high-temperature resolution, short sampling intervals and short time intervals for temperature monitoring in the sand model. In the system, the small variation in the temperature due to groundwater flow was detected. The numerical analysis was conducted for both the seepage process and the heat transfer progression in the sand model. The results of the heat flow simulation were evaluated and compared with the measured temperature by the optical fiber DTS. Obvious temperature reduction was obtained due to seepage propagation in the sand. The rate of temperature reduction was observed to be dependent on the seepage flow velocity. Full article

(This article belongs to the Special Issue Advances in Groundwater and Surface Water Monitoring and Management)

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25 pages, 52915 KiB

Open AccessArticle

Hydrogeological Characterization of Coastal Aquifer on the Basis of Observed Sea Level and Groundwater Level Fluctuations: Neretva Valley Aquifer, Croatia

by Veljko Srzić, Ivan Lovrinović, Ivan Racetin and Fanito Pletikosić

Water 2020, 12(2), 348; https://doi.org/10.3390/w12020348 - 26 Jan 2020

Cited by 15 | Viewed by 4942

Abstract

Hydrogeological data availability is often limited to local areas where usual in situ tests or methods are applied (slug/bail or pumping tests, Electrical Resistivity Tomography (ERT)). Because most problems (e.g., saltwater intrusion mitigation) require problem analysis on larger scales (catchment or sub catchment), [...] Read more.

Hydrogeological data availability is often limited to local areas where usual in situ tests or methods are applied (slug/bail or pumping tests, Electrical Resistivity Tomography (ERT)). Because most problems (e.g., saltwater intrusion mitigation) require problem analysis on larger scales (catchment or sub catchment), hydrogeological identification of global character is preferable. This work leads to the determination of aquifer hydrogeological parameters on the basis of observed sea level, groundwater piezometric head found inland, and barometric pressure. When applied to observed signals, the approach led efficiently to final hydrogeological characterization. After identification of dominant tidal constituents from observed signals, barometric efficiency was successfully determined. Following available information on geological settings, an appropriate conceptual model was applied and updated to count for polychromatic signals. Final determination of hydrogeological parameters relied on root mean square error (RMSE) minimization and led to determination of (i) presence of three stratigraphic units: unconfined sandy aquifer on the top, a confining layer made of clay, and a confined gravel layer; (ii) existence of the clay layer under the sea with a total length of 1400 m; (iii) a clay layer has been identified as confining one by both spectral analysis and determined leakance value; and (iv) estimated confined aquifer specific storage ranging from 2.87 × 10⁻⁶ to 4.98 × 10⁻⁶ (m⁻¹), whereas hydraulic conductivity ranged from 7.0 × 10⁻⁴ to 7.5 × 10⁻³ (m s⁻¹). Both range intervals corresponded to previous in situ findings conducted within the area of interest. Full article

(This article belongs to the Special Issue Advances in Groundwater and Surface Water Monitoring and Management)

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20 pages, 4418 KiB

Open AccessArticle

Optimal Design and Prediction-Independent Verification of Groundwater Monitoring Network

by Sreekanth Janardhanan, Dan Gladish, Dennis Gonzalez, Dan Pagendam, Trevor Pickett and Tao Cui

Water 2020, 12(1), 123; https://doi.org/10.3390/w12010123 - 30 Dec 2019

Cited by 9 | Viewed by 3322

Abstract

In this study, we developed a workflow that applies a complex groundwater model for purpose-driven groundwater monitoring network design and uses linear uncertainty analysis to explore the predictive dependencies and provide insights into the veracity of the monitoring design. A numerical groundwater flow [...] Read more.

In this study, we developed a workflow that applies a complex groundwater model for purpose-driven groundwater monitoring network design and uses linear uncertainty analysis to explore the predictive dependencies and provide insights into the veracity of the monitoring design. A numerical groundwater flow model was used in a probabilistic modelling framework for obtaining the spatial distribution of predicted drawdown for a wide range of plausible combination of uncertain parameters pertaining to the deep sedimentary basin and groundwater flow processes. Reduced rank spatial prediction was used to characterize dominant trends in these spatial drawdown patterns using empirical orthogonal functions (EOF). A differential evolution algorithm was used to identify optimal locations for multi-level piezometers for collecting groundwater pressure data to minimize predictive uncertainty in groundwater drawdown. Data-worth analysis helps to explore the veracity of the design by using only the sensitivities of the observations to predictions independent of the absolute values of predictions. A 10-bore monitoring network that collects drawdown data from multiple depths at each location was designed. The data-worth analysis revealed that the design honours sensitivities of the predictions of interest to parameters. The designed network provided relatively high data-worth for minimizing uncertainty in the drawdown prediction at locations of interest. Full article

(This article belongs to the Special Issue Advances in Groundwater and Surface Water Monitoring and Management)

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15 pages, 5181 KiB

Open AccessArticle

High Resolution Monitoring of Seawater Intrusion in a Multi-Aquifer System-Implementation of a New Downhole Geophysical Tool

by Adi Tal, Yishai Weinstein, Matthieu Baïsset, Arik Golan and Yoseph Yechieli

Water 2019, 11(9), 1877; https://doi.org/10.3390/w11091877 - 9 Sep 2019

Cited by 10 | Viewed by 3327

Abstract

Monitoring of seawater intrusion is extremely important for the management of coastal aquifers, and therefore requires reliable and high-frequency monitoring tools. This paper describes the use of a new near field and downhole geophysical tool that monitors seawater intrusion in boreholes with high [...] Read more.

Monitoring of seawater intrusion is extremely important for the management of coastal aquifers, and therefore requires reliable and high-frequency monitoring tools. This paper describes the use of a new near field and downhole geophysical tool that monitors seawater intrusion in boreholes with high vertical resolution. This sensor is further used to study the impact of pumping on water electrical conductivity profiles (ECP) at the fresh-saline water interface. The new device was installed in a confined calcareous sandstone aquifer along the northern Israeli coast. The site includes two monitoring wells and one pumping well located at distances of 50, 75 and 125 m from shoreline, respectively. The new geophysical tool, called the subsurface monitoring device (SMD), was examined and compared to water an electric conductivity profiler (ECP) and a conductivity temperature depth (CTD) driver’s data. All methods show similar salinity trends, and changes in pumping regime were clearly identified with both the SMD and CTD. The advantage of using the SMD tool is the high temporal and spatial resolution measurement, which is transferred via internet and can be analyzed and interpreted in real time. Another advantage of the SMD is that it measures the electrical resistivity of the aquifer mostly outside the well, while both water ECP and the CTD measure in-well electrical conductivity; therefore, are subjected to the artefact of vertical flow in the well. Accordingly, while the CTD shows an immediate and sharp response when pumping is stopped, the SMD provides a gradual electric conductivity (EC) change, demonstrating that stability is reached just after a few days, which illustrates, more precisely, the hydrological response of the aquifer. Full article

(This article belongs to the Special Issue Advances in Groundwater and Surface Water Monitoring and Management)

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12 pages, 3712 KiB

Open AccessArticle

Increase and Spatial Variation in Soil Infiltration Rates Associated with Fibrous and Tap Tree Roots

by Dashuai Zhang, Zhaogeng Wang, Qizhong Guo, Jijian Lian and Liang Chen

Water 2019, 11(8), 1700; https://doi.org/10.3390/w11081700 - 16 Aug 2019

Cited by 20 | Viewed by 4941

Abstract

Trees play important roles in urban stormwater management; through the loosening of soils by root growth, they increase infiltration and reduce runoff, helping to mitigate flooding and recharge groundwater. Malus baccata with fibrous roots and Sophora japonica with tap roots were studied experimentally [...] Read more.

Trees play important roles in urban stormwater management; through the loosening of soils by root growth, they increase infiltration and reduce runoff, helping to mitigate flooding and recharge groundwater. Malus baccata with fibrous roots and Sophora japonica with tap roots were studied experimentally to assess their enhancement of soil infiltration. A blank test without a tree was conducted for comparison. Steady-state soil infiltration rates at the bottom of test tanks were measured as 0.28 m/d, 0.33 m/d, and 0.61 m/d for the blank test, M. baccata, and S. japonica, respectively. This represents a 19% increase in the infiltration rate by planting M. baccata and a 118% increase by planting S. japonica. A larger increase in the infiltration rate by S. japonica is consistent with the effects of deeper and more vertical roots that help loosen deeper soils. Spatial variations in soil infiltration rates were also measured. Infiltration rates for M. baccata (1.06 m/d and 0.62 m/d) were larger than those for S. japonica (0.91 m/d and 0.51 m/d) at the same depths (0.35 m and 0.70 m); this is consistent with the expected effects of the shallower and more lateral roots of M. baccata. This study furthers our understanding of the roles of trees in watersheds and urban environments. Full article

(This article belongs to the Special Issue Advances in Groundwater and Surface Water Monitoring and Management)

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18 pages, 5297 KiB

Open AccessArticle

Determining the Relation between Groundwater Flow Velocities and Measured Temperature Differences Using Active Heating-Distributed Temperature Sensing

by Wiecher Bakx, Pieter J. Doornenbal, Rebecca J. van Weesep, Victor F. Bense, Gualbert H. P. Oude Essink and Marc F. P. Bierkens

Water 2019, 11(8), 1619; https://doi.org/10.3390/w11081619 - 5 Aug 2019

Cited by 16 | Viewed by 4479

Abstract

Active Heating-Distributed Temperature Sensing (AH-DTS) has the potential to allow for the measurement of groundwater flow velocities in situ. We placed DTS fiber-optic cables combined with a heating wire in direct contact with aquifer sediments in a laboratory scale groundwater flow simulator. Using [...] Read more.

Active Heating-Distributed Temperature Sensing (AH-DTS) has the potential to allow for the measurement of groundwater flow velocities in situ. We placed DTS fiber-optic cables combined with a heating wire in direct contact with aquifer sediments in a laboratory scale groundwater flow simulator. Using this setup, we empirically determined the relationship between

Δ T

, the temperature difference by constant and uniform heating of the DTS cable and the background temperature of the groundwater system, and horizontal groundwater flow velocity. Second, we simulated the observed temperature response of the system using a plan-view heat transfer flow model to calibrate for the thermal properties of the sediment and to optimize cable setup for sensitivity to variation in groundwater flow velocities. Additionally, we derived an analytical solution based on the heat flow equation that can be used to explicitly calculate flow velocity from measured

Δ T

for this specific AH-DTS cable setup. We expect that this equation, after calibration for cable constitution, is valid for estimating groundwater flow velocity based on absolute temperature differences measured in field applications using this cable setup. Full article

(This article belongs to the Special Issue Advances in Groundwater and Surface Water Monitoring and Management)

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20 pages, 2585 KiB

Open AccessReview

Management of Seawater Intrusion in Coastal Aquifers: A Review

by Mohammed S. Hussain, Hany F. Abd-Elhamid, Akbar A. Javadi and Mohsen M. Sherif

Water 2019, 11(12), 2467; https://doi.org/10.3390/w11122467 - 24 Nov 2019

Cited by 129 | Viewed by 21860

Abstract

Seawater intrusion (SWI) is one of the most challenging and widespread environmental problems that threaten the quality and sustainability of fresh groundwater resources in coastal aquifers. The excessive pumping of groundwater, associated with the lack of natural recharge, has exacerbated the SWI problem [...] Read more.

Seawater intrusion (SWI) is one of the most challenging and widespread environmental problems that threaten the quality and sustainability of fresh groundwater resources in coastal aquifers. The excessive pumping of groundwater, associated with the lack of natural recharge, has exacerbated the SWI problem in arid and semi-arid regions. Therefore, appropriate management strategies should be implemented in coastal aquifers to control the impacts of SWI problems, considering acceptable limits of economic and environmental costs. The management of coastal aquifers involves the identification of an acceptable ultimate landward extent of the saline water body and the calculation of the amount of seaward discharge of freshwater that is necessary to keep the saline–freshwater interface in a seacoast position. This paper presents a comprehensive review of available hydraulic and physical management strategies that can be used to reduce and control SWI in coastal aquifers. Advantages and disadvantages of the different approaches are presented and discussed. Full article

(This article belongs to the Special Issue Advances in Groundwater and Surface Water Monitoring and Management)

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20 pages, 4768 KiB

Open AccessCase Report

Optimized Pumping Strategy for Reducing the Spatial Extent of Saltwater Intrusion along the Coast of Wadi Ham, UAE

by Modou A. Sowe, Sadhasivam Sathish, Nicolas Greggio and Mohamed M. Mohamed

Water 2020, 12(5), 1503; https://doi.org/10.3390/w12051503 - 24 May 2020

Cited by 7 | Viewed by 3933

Abstract

Many coastal aquifers are facing severe anthropogenic impacts such as urbanization, industrialization and agricultural activities are resulting in a saltwater intrusion. This establishes the need for a sustainable groundwater management strategy aimed to overcome the situation. Pumping of brackish/saline water to mitigate saltwater [...] Read more.

Many coastal aquifers are facing severe anthropogenic impacts such as urbanization, industrialization and agricultural activities are resulting in a saltwater intrusion. This establishes the need for a sustainable groundwater management strategy aimed to overcome the situation. Pumping of brackish/saline water to mitigate saltwater intrusion is a major potential approach to effectively control saltwater intrusion. However, this method has many challenges including selection of appropriate discharge rates under an optimum number of pumping wells and at specified wells distance from the shoreline. Hence, this study developed a Finite Element Flow and solute transport model (FEFLOW) to simulate three scenarios to assess the most appropriate pumping rates, number of wells and optimum well locations from the shoreline. These parameters were assessed and evaluated with respect to the change in groundwater saline concentration at different distance from the coastline. The 15,000 mg L⁻¹ isosalinity contour line was used as a linear threshold to assess the progression of saltwater intrusion along three major locations in the aquifer. Scenario One was simulated with a constant number of wells and rate of pumping. Shifting of pumping wells to several distances from the shoreline was conducted. Scenario Two assessed the most appropriate number of pumping wells under constant pumping rates and distances from the shoreline and in scenario 3, the optimum pumping rates under a constant number of wells and distance from the shoreline were simulated. The results showed that the pumping of brackish/saline water from a distance of 1500 m from the shoreline using 16 pumping wells at a total pumping rate of 8000 m³ d⁻¹ is the most effective solution in contrasting the saltwater intrusion in the Wadi Ham coastal aquifer. Full article

(This article belongs to the Special Issue Advances in Groundwater and Surface Water Monitoring and Management)

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