Hydrogeology Journal最新文献

Abstract

Groundwater-level monitoring networks provide vital information for hydrogeological studies. Including exploited domestic wells in these monitoring networks can provide a low-cost means of obtaining a broader set of data; however, the use of these sites is limited because the frequent pumping of these wells generates outliers in the recorded time series. Here a slope criterion is applied to identify and remove outliers from groundwater-level time series from exploited domestic wells. Nonetheless, eliminating outliers creates a problem of missing values, which biases the subsequent time series analysis. Thus, 14 imputation methods were used to replace the missing values. The proposed approach is applied to groundwater-level time series from a monitoring network of 20 wells in the Lanaudière region, Québec, Canada. The slope criterion proves very effective in identifying outliers in exploited domestic wells. Missing values generated by outlier removal can reach up to 99% of the recorded data. Among the characteristics of the missing value pattern, the gap size and the position of the gaps along the time series are the most important parameters that affect the performance of the 14 imputation methods. Of the imputation methods tested, linear interpolation and Stineman interpolation, and then Kalman filtering, were the most effective. The present study demonstrates that exploited domestic wells can be used for groundwater monitoring by removing the outliers and imputing the missing values.

The origin and setting of the extensive aquifer systems that underlie Jakarta (the capital city of Indonesia), and the impacts that have resulted from their largely unchecked exploitation, are described. The ready availability of groundwater has been key to the city’s growth and prosperity, but it has come at a cost. Jakarta is now the most rapidly subsiding capital city in the world and subject to frequent flooding. These impacts have become major factors in the decision to relocate to a new capital city, named Nusantara, currently under construction on the island of Borneo.

The high groundwater salinity of crystalline aquifers in semiarid areas is generally attributed to the dissolution and leaching of meteoric salts that have been progressively evapoconcentrated in the different hydrological compartments under dry climate conditions. A numerical model, simulating water and salt balances, was developed from a case study in Northeast Brazil to: (1) test the validity of this hypothesis, through the quantification of all relevant water cycle processes in the studied watershed, and (2) demonstrate how changes in land cover can impact groundwater salinity. Computations showed that the aridity and the high evapo(transpi)ration rates from the unsaturated zone and/or surface water (ponds, reservoirs) cannot lead to the observed aquifer salinization levels, but only to concentrations of a few tens or hundreds of mg L^–1 (Cl^–). The only process that can induce a high groundwater salinity, with chloride concentrations up to several g L^–1, is the transpiration of groundwater by the deep roots of the vegetation, with a rate reaching 100% of the annual recharge. In this case study, the vegetation involved is the native Caatinga forest. Simulations of the long-term dynamics of groundwater salinity indicate that aquifer areas with high salinity are relicts of the Caatinga pre-colonization period during which subterranean endorheic conditions were prevailing. Following the Caatinga deforestation linked to colonial agricultural development, aquifer recharge increased and endorheism ceased. Consequently, these aquifers may have now been experiencing a desalination process for about three centuries. The desalination spatial variability drivers are explained in the paper.

In a changing world, long datasets for groundwater have great value, as they do for all components of environmental monitoring. However, there is a global scarcity of such datasets, with few extending beyond 30 years and even fewer to 50 or 100 years. Hydrogeological investigations and groundwater management activities benefiting from long-term data are listed, the successful use of such datasets illustrated, and the reasons for their scarcity discussed.

A novel well-log-analysis approach is presented for an improved prediction of petrophysical properties in groundwater formations. Geophysical well logs are simultaneously processed for quantifying the lithology, storage capacity, and water flow parameters. A fully automated data processing workflow is proposed, the feasibility of which is assured by an appropriate starting model set by the joint application of factor analysis and the Hurst exponent, and a solution of a highly overdetermined inverse problem. The Hurst exponent is used for zone boundary detection, which assists the series expansion-based interval inversion method applied for estimation of the petrophysical parameters of clastic formations. The hydraulic conductivity as a well log is directly derived from the inversion results. The workflow is tested using both synthetic data contaminated with 5% Gaussian distributed noise and real data collected from a thermal water well in Baktalórántháza, eastern Hungary. At the test site, the Hurst exponent extracted from the wireline logs allows one to divide the processed interval into subzones around the Pleistocene-Miocene boundary. The observed wireline logs are inverted to estimate the volumetric parameters (porosity, shale content, water saturation, etc.) of the same zones. The predicted parameters, including hydraulic conductivity, reveal that Pleistocene sediments contain good aquifers with formation quality varying with depth. The shale volume and hydraulic conductivity logs show a proper match with the core data, which confirms the results of the comprehensive analysis. The suggested workflow is recommended for the evaluation of groundwater formations located in different depth domains, from unsaturated sediments to geothermal reservoirs.

Scarce rainfall and strong evaporation add complexities to estimating groundwater recharge in arid and semiarid regions. There are still many gaps in the understanding of how soil water near the ground surface interacts with the atmosphere, which increases the difficulties of determining the contribution of rainfall to groundwater in these regions. This study used a weighing lysimeter to observe the potential recharge over a 1-year period in the Mu Us Desert, northwest China. The observed data were used to explore the infiltration processes and to quantify recharge. The results show: (1) no potential recharge can be observed if the rainfall is less than 12.3 mm/day during the experimental period. The observed annual potential recharge was 29.3 mm, which accounted for 10% of the annual rainfall. (2) The threshold of soil-water content for potential recharge was determined, such that when the average soil moisture along the soil profile (0–100 cm) is larger than 0.12 cm³/cm³, the potential recharge can be observed. (3) The empirical weight function (Poisson distribution) method performed well in the estimation of recharge compared to the observed lysimeter data. In addition, the parameter γ of the Poisson distribution has a linear relationship with the average soil-water content along the soil profile. These findings can help researchers understand recharge, which has significance in groundwater resource management.

Heihe River is the second largest inland river in China, but groundwater is the main source of water in the middle reaches of the Heihe River Basin (HRB). The middle reaches of HRB consists of Zhangye and Jiuquan basins. In view of deficiencies in the groundwater exploration techniques, methods, and accuracy associated with previous studies in the HRB, this study used stratified groundwater exploration (monitoring and sampling) techniques to identify the groundwater flow systems. Three fields were considered—groundwater flow dynamics, temperature, and chemical. The results show that stratified groundwater-level monitoring technology can be used to quickly identify groundwater recharge and discharge areas. The main groundwater recharge area in the HRB’s middle reaches is in the piedmont plain, and most of the rest of this middle basin comprises groundwater runoff areas and discharge areas. Shallow groundwater temperatures (average and variation) reflect the characteristics of groundwater recharge, runoff, and discharge. The shallow groundwater temperature gradually increased from the recharge area to the discharge area, and the temperature annual variation tended to be greatest in the central area. Along the direction of groundwater flow, the δD content of shallow groundwater in the HRB’s middle reaches initially increased and then decreased, and the δD content of groundwater in the vertical direction decreased gradually from shallow to deep. The surface-water/groundwater exchange in the central Zhangye Basin mainly occurred in the shallow areas, within 200 m depth. Thus, stratified groundwater exploration technology is helpful for identifying groundwater flow systems in inland arid basins.

To achieve its ambitious plans to reclaim its deserts through mega projects, Egypt is heavily relying on fossil or little-recharged groundwater. This article revisits the results and methodologies of the studies conducted over the last two decades on groundwater management and uses in the Western Desert. Most previous studies aimed at simulating different groundwater abstraction scenarios by modeling local areas in aquifer systems, but with poor definitions of boundary conditions and limited historical data. Studies were constrained by the unavailability of data, access difficulties, and high collection costs in desert lands. Thus, to propose reliable sustainable groundwater resources development plans and recommendations for future protection strategies, an open-access monitoring network representing regional aquifers is needed. More investigations based on extensive field visits are essential to monitor environmental, economic, and social conditions, identify constraints, and learn lessons for reclaiming desert lands. Moreover, this review highlighted the need to frame a rational strategy for the long-term sustainable exploitation of non-renewable groundwater in the aquifer systems of Egypt and develop an appropriate exit strategy for desert communities in case of serious water resource depletion.

Depth-wise variation in hydraulic structures of volcanic aquifers is rarely investigated when compared to basement and other rocks. A comprehensive dataset is presented here on the hydraulic properties of volcanic aquifers from a large igneous province in Africa. Age- and depth-wise variation in transmissivity (T), yield (Q), hydraulic conductivity (K) and specific capacity (S_c) of volcanic aquifers and water wells were systematically examined for stratigraphic units of various ages (Eocene to Quaternary Period) and well depth (18–882 m). The T ranges from 0.02 to 9,830 m²/day. There is a good correlation between the age of the emplacement of the rocks and their hydraulic properties. The oldest (Eocene) basalts show lower productivity (T, K and Q) when compared to the youngest (Quaternary) basalts. There is no statistically significant depth-wise variation of T, K and Q when one single formation is investigated. The insights gained from the analysis show that increasing the depth of drilling does not necessarily increase aquifer yields and can inform global-scale groundwater modelling efforts. The data challenge the widely held assumption that K and Q decrease with depth. Unlike basement rocks, volcanic rocks show no statistically significant change in hydraulic properties along its depth profile to the depth of 900 m.