Water-level Contours Research Articles

Гүний Хоолойн газар доорхи усны ашиглалтын нөлөө

Comparative methods and the last decade of daily data were used estimate the relationship between precipitation and groundwater level response, and to analyze the consumption influence on confined aquifers in Gunii khooloi groundwater deposit, Umnugovi province, Mongolia.We have synthesized all the available data derived from the monitoring studies as well as carried out field measurements in this study. As a result of the monitoring study, water level of confined aquifer has been decreasing since 2011 related to the water consumption. There is a small depression cone in the eastern part of the area. According to the water level contour of 2013, groundwater level in confined aquifer near to the pumping well in the central part has been fluctuated and decreased about 10m. But it is observed that water level fluctuation is relatively stabilized from the 2015.

Groundwater hydrodynamics and sustainability of Addis Ababa city aquifer

In the past two decades, Addis Ababa city has been under continuous demand of additional water supply improvement due to critical shortage of supply became particularly a serious problem at the outskirts of topographically high places. In order to overcome the existing problem, groundwater development optioned as emergency water supply project. However, the development continued without giving attention to its sustainability and now takes about 63% of the share. Over the last decade, many well-fields have been drilled; Akaki, Legedadi-Legetafo-Ayat, South-Ayat-North-Fanta, and Addis Ababa pocket areas in the same watershed that have an area about 1490 km2. The main objective of this study was to assess the groundwater hydrodynamics and sustainable utilization of the sources. For the study, 166 deep borehole completion and pumping test well fields within and around Addis Ababa were used. From the analysis it was found that hydraulic conductivity and transmissivity in the watershed vary from 0.02 to 256 m/day and 5.4 × 101 to 2.16 × 104 m2/day respectively. The major aquifers are fractured & scoriaceous basalt, scoria, fractured ignimbrite or a combination of these rocks. Analysis of water level contour map for Akaki well-field indicated that 84.50% of the current pumping water levels were below the dynamic water level. In particular, old Akaki well-field has been severely depleted. Out of 24 drilled wells, 13 of them are abandoned as water level and discharge have significantly declined. Despite huge importance of groundwater, it has been understood poorly and undervalued. It is a finite resource and the aquifers can become depleted as this extraction rates which exceed recharge rates. Therefore, groundwater management should be practiced through reliable aquifer characterization, sustainable development, planning of conjunctive use of surface water and artificial recharge.

Static Water Level and Elevation Analyses of Shallow Hand-Dug Wells in Ilorin Metropolis, Nigeria

Aim: This study was conducted to reveal the depth to water level and surface elevation in selected hand-dug wells within Ilorin metropolis to assist in planning and management of water resources within the study area.
 Place and Duration of Study: The study was conducted in Ilorin metropolis, North Central, Nigeria.
 Methodology: A total of twenty-six (26) hand-dug wells were sampled and relevant spatial information was acquired using a handheld GPS; data collected include: longitude, latitude, elevation and depth to water, then the static water level above sea level was estimated by the difference between depth to water and elevation. Statistical analyses such as mean and standard deviation were determined, also a base map, contour maps and 3-D elevation model of the study area were produced using ArcGIS 10.4 and Surfer 10 software.
 Results: The depth to water within the study area ranges between 1.6 m and 13.3m, while elevation were between 284.1 m and 377.9 m, then the static water level ranges between 270.8 m and 371.4 m. The static water level contour map showed a radial and multidimensional groundwater flow pattern trending in the NE–SW and NW–SE directions while the 3-D elevation model revealed an undulating terrain.
 Conclusion: The study concluded that the depth to groundwater is relatively shallow and this can guide proper development and management of groundwater resources within the metropolis.

Modelling Groundwater Hydraulics to Design a Groundwater Level Monitoring Network for Sustainable Management of Fresh Groundwater Lens in Lower Indus Basin, Pakistan

The over-extraction of groundwater from thin fresh groundwater lenses is a threat to the livelihood of farmers in the Lower Indus Basin (LIB). It is essential to monitor and regulate this pumping to sustain fresh groundwater lenses. In this study, we applied a modelling approach in combination with geostatistical analysis to identify the critical locations to monitor the groundwater levels for sustaining fresh groundwater in the LIB. Our approach included four steps: (i) simulating temporal heads using a calibrated hydrogeological model; (ii) sampling monitoring locations using a hexagonal pattern of sampling; (iii) applying principal component analysis (PCA) of the temporal head observations, and selecting high scoring locations from the PCA; and (iv) minimizing the observation points to represent the water level contours. The calibrated model was able to replicate the hydro-dynamic behavior of the study area, with a root mean square of 0.95 and an absolute residual mean of 0.74 m. The hexagonal pattern of spatial sampling resulted in a 195 point network, but PCA reduced this network to 135 points and contour classification reduced it even further to 59 points. The 195, 135, and 59 point networks represented the water levels with average standard errors of 0.098, 0.318, and 0.610 m, respectively. Long-term simulations with increased pumping showed that the water levels would best be assessed by 195 monitoring points, although 135 and 59 points would represent the depleting area but would not capture the water logging area.

An Assessment of Groundwater Grab Syndrome in Langata Sub County, Nairobi City-Kenya

Interest on the investigation of groundwater depletion threat is growing globally and Langata sub County in Nairobi, the capital city of the Republic of Kenya, is not an exception. Because of drought-induced water shortage, households in Langata do rely on borehole water to augment their intermittent municipal water supply system. Consequently, there is an upsurge of borehole developments as drought events unfold. Previous studies here have focused on impact of borehole depths and density yet little seems to have been done to compute the correlation coefficient between drought events data and historical borehole development records as an assessment for groundwater “grab” syndrome. This study used drought index computation method (SPI) alongside other statistical methods to seek the answer to the problem. Using 57 years of monthly rainfall data and 26 years of borehole development data, the study established that, there is a positive correlation coefficient. Similarly, a trend analysis of borehole drilling and struck water level depths indicated a positive parallel rising trend on both. Further, when the borehole distribution map and struck water level contour maps were plotted, a sign of a probable well interference during pumping was detected, which however, requires a new investigation to confirm the syndrome of groundwater depletion threat. The study has contributed to the groundwater depletion research by deploying statistical research methods for risk detection. Finally, the study has proposed for a new groundwater management policy that will encourage initiation of artificial recharge schemes for the study site and beyond.

Construction of Water Table Contour Map and Geo Hydrological Studies on Krishnagiri Using GIS Techniques

Geo-hydrology and groundwater exploration manner to pick out and to find the zone of recharge of groundwater in a precise river basin or a catchment .water level contour traces (or waft traces) are much like topographic strains on a map. They fully represent "elevations" in the subsurface. Water table contour lines can be used to inform which manner groundwater will glide in a given region. Plenty of wells are drilled and the hydraulic head is measured in each one. Water desk contours are drawn that be a part of areas of identical head .The ones water table contours lines are also called equipotential strains. Bear in mind: groundwater usually movements from a place of the higher hydraulic head to an area of decrease hydraulic head, and perpendicular to equipotential traces. In our challenge, we put into effect concept of water table contour map and geohydrological studies on Krishnagiri using GIS software program which plays the essential position in contemporary technology.

GIS based approach to understand the factors influencing the water level of the coastal aquifers in the ramnad district, Tamilnadu, India

An attempt has been made in this study to understand the factors influencing the variation in water level of the groundwater of the Ramnad district. The different factors considered for study were average water level, Land use pattern, tanks and rainfall pattern of the study area. The water level contours were spatially plotted for four months interval and their average was considered for comparison. The rainfall trend of the district was obtained by the Thiessen polygon method. Further the Average water level contour was overlaid over the land use, tanks and rainfall distribution maps to understand the spatial influencing factor and it was identified that the agricultural return flow and the tank intensity play a major role in the recharge of the groundwater of this coastal aquifers.

KT3D_H2O: A Program for Kriging Water Level Data Using Hydrologic Drift Terms

It is often necessary to estimate the zone of contribution to, or the capture zone developed by, pumped wells: for example, when evaluating pump-and-treat remedies and when developing wellhead protection areas for supply wells. Tonkin and Larson (2002) and Brochu and Marcotte (2003) describe a mapping-based method for estimating the capture zone of pumped wells, developed by combining universal kriging (kriging with a trend) with analytical expressions that describe the response of the potentiometric surface to certain applied stresses. This Methods Note describes (a) expansions to the technique described by Tonkin and Larson (2002); (b) the concept of the capture frequency map (CFM), a technique that combines information from multiple capture zone maps into a single depiction of capture; (c) the development of a graphical user interface to facilitate the use of the methods described; and (d) the integration of these programs within the MapWindow geographic information system environment. An example application is presented that illustrates ground water level contours, capture zones, and a CFM prepared using the methods and software described.

Using Synthetic Data and Artificial Wells to Teach the Construction and Use of Water Level Contour Maps

Contour maps that depict groundwater levels (e.g., water table maps and potentiometric surface maps) are essential to the practice of hydrogeology. However, there are significant barriers to effectively teaching students how to create and interpret such maps. Barriers to instruction include the logistics of accessing real wells, assuring that students are provided with a challenging problem, and the lack of a unique solution. We present a new approach that overcomes these barriers through the use of artificial wells and synthetic data. Our approach provides students with a challenging problem that takes them through the whole process, from data collection to interpretation of the resulting maps. In the end, students are able to see how their efforts compare to a known solution, rather than another estimate. Students are also able to choose locations for additional wells that they believe will enhance their ability to create an accurate map. These qualities lead to a substantial improvement in student comprehension over instructional approaches that are based on existing data or limited field measurements.

Inverse geochemical modeling of groundwater evolution with emphasis on arsenic in the Mississippi River Valley alluvial aquifer, Arkansas (USA)

Inverse geochemical modeling (PHREEQC) was used to identify the evolution of groundwater with emphasis on arsenic (As) release under reducing conditions in the shallow (25–30 m) Mississippi River Valley Alluvial aquifer, Arkansas, USA. The modeling was based on flow paths defined by high-precision (±2 cm) water level contour map; X-ray diffraction (XRD), scanning electron microscopic (SEM), and chemical analysis of boring-sediments for minerals; and detailed chemical analysis of groundwater along the flow paths. Potential phases were constrained using general trends in chemical analyses data of groundwater and sediments, and saturation indices data (MINTEQA2) of minerals in groundwater. Modeling results show that calcite, halite, fluorite, Fe oxyhydroxide, organic matter, H2S (gas) were dissolving with mole transfers of 1.40E − 03, 2.13E − 04, 4.15E − 06, 1.25E + 01, 3.11, and 9.34, respectively along the dominant flow line. Along the same flow line, FeS, siderite, and vivianite were precipitating with mole transfers of 9.34, 3.11, and 2.64E − 07, respectively. Cation exchange reactions of Ca2+ (4.93E − 04 mol) for Na+ (2.51E − 04 mol) on exchange sites occurred along the dominant flow line. Gypsum dissolution reactions were dominant over calcite dissolution in some of the flow lines due to the common ion effect. The concentration of As in groundwater ranged from <0.5 to 77 μg/L. Twenty percent total As was complexed with Fe and Mn oxyhydroxides. The redox environment, chemical data of sediments and groundwater, and the results of inverse geochemical modeling indicate that reductive dissolution of Fe oxyhydroxide is the dominant process of As release in the groundwater. The relative rate of reduction of Fe oxyhydroxide over SO42- with co-precipitation of As into sulfide is the limiting factor controlling dissolved As in groundwater.

What Is a Plume? and Why Do I Care?

What Is a Plume? and Why Do I Care?

Development of groundwater modeling for the Azraq Basin, Jordan

The three-dimensional groundwater flow model MODFLOW was applied to simulate water level change in the complex multi-aquifer systems (the Upper and Middle Aquifers) of the Azraq basin. The model was calibrated by matching observed and simulated drawdown for steady and transient states over the period 1970–1992. Drawdown data for the period 1993–1997 were used to test the model's ability to predict the response of the aquifers. The model performed well in representing the water level contours of the Upper and Middle Aquifers for steady state calibration. Agreement between the observed and simulated drawdowns was obtained for transient state calibration. To predict the aquifer system responses for the period of 1997–2025, four different pumping schemes (scenarios) have been investigated. The first scenario (present pumping rate) reveals that there will be approximately a 25 m drop in the water level at the well-field area in 2025. However, the worst scenario (pumping rate at 1.5 times the present rate) reveals an approximate 39 m drop in the water level at the well-field area in 2025. The safe yield for the Upper Aquifer System was found to be about 25 million cubic meters (MCM) yearly.

On the Rio Grande Aquifer: Flow Relationships, Salinization, and Environmental Problems From El Paso to Fort Quitman, Texas

The Rio Grande floodplain between the City of El Paso and Fort Quitman, Texas (70 mi [113 km] reach) varies from intensively urbanized (first 20 mi [32 km]), to intensively irrigated by surface and ground water (next 40 mi [65 km]), to sparsely inhabited and little developed (last 10 mi [16 km]). Water-level contour maps prepared with recent and historical data illustrate losing stream, underflow, and baseflow conditions on different segments of the alluvial floodplain. The condition of losing stream is apparent along the urbanized zone where draw-down cones from municipal well fields have reversed the hydraulic gradient between the river and the Rio Grande aquifer. Aquifer flow varies from underflow to gaining stream downstream from the urbanized zone. Hydrochemistry of the Rio Grande aquifer evolves downstream from a Na-Ca-mixed anion type water with TDS mostly between 1,000 and 3,500 mg/L to a Na-Ca-SO 4 -Cl type water with TDS mostly between 3,000 to 6,000 mg/L. Plots of 2 H vs 18 O for ground-water samples collected in the Mexican part of the Rio Grande aquifer follow an evaporation trend. The most enriched samples correspond to higher salinity and greater distances downstream. Monthly water-quality data from the Rio Grande show similar changes in hydrochemistry. Increasing salinity in both the Rio Grande and Rio Grande aquifer generally reflect the tendency for salts to be recycled in irrigation water, to return to the Rio Grande, and then to be reapplied to crops. By this process the salinities in the Rio Grande and Rio Grande aquifer increase in a continuous manner downstream. Other existing and potential water-quality problems in the Rio Grande and Rio Grande aquifer include fecal coliform bacteria, nitrate, pesticides, and organic contaminants. These are a concern because of cross-formational flow between the Rio Grande aquifer and the Hueco Bolson aquifer, the latter a source of water for more than 1.6 million residents along the El Paso/Ciudad Juarez corridor.

Integrating GIS and RDBMS technologies during construction of a regional groundwater model

Finite difference groundwater flow models like MODFLOW require cell-by-cell averages for a myriad of parameters. In reality, the data a modeller uses comes from many sources in a variety of formats. Point measurements from boreholes are a critical dataset and can be combined with lines (eg water level and structural contours), polygons (eg surface geology and land use maps) and rasters (eg Landsat imagery). Firstly, the modeller needs a working environment to store, integrate and analyse these datasets and to derive the cell-by-cell model input. Secondly, the model output needs to be compared with the original source data that describes the real world. Borehole information is typically stored in a relational database management system (RDBMS) and geographic information systems (GIS) are designed for managing spatial information. These technologies have been used as the working environment for the Lower Darling model, which is a large regional groundwater flow model within the Murray Geological Basin, southeast Australia. Different strategies were developed to manipulate the available data into MODFLOW input files and also for the modelled heads and flows to be compared with field observations. Some of these strategies are specific to the Lower Darling model, but others are generic and can be easily applied in the data manipulation and calibration of groundwater models for regional aquifer systems.

The use of stable isotope tracers for the estimation of the direction of groundwater flow

Spatial variation in the stable isotopic composition of groundwater is indicative of mixing of waters of different stable isotopic content. Infiltration losses from a river or lake are examples which result in a positive correlation with distance from the source of infiltration to the groundwater. This technical note describes a method for determining the direction of groundwater flow. The regression is determined of either 18O or deuterium against distance along the X-coordinate of each sampling location. This computation is made for given intervals, for example 5 degrees, of rotation of the axes through 180 degrees. The angle of rotation which results in the maximum value of the correlation coefficient determines the direction of groundwater flow. This approach is applied to field studies in Ecuador and the Republic of Korea. In the latter case the estimated direction of flow agreed with the resultant of the two flow vectors obtained from water level contours.

Electrical resistivity and seismic refraction studies for groundwater in the Jodhpura area, Rajasthan

The results of geophysical investigations carried out for groundwater employing seismic refraction and electrical resistivity methods near Jodhpura (27o47′30″N:75o42′40″E) in the Jhunjhunu District, Rajasthan, are presented. Prominent resistivity low zones, revealed by the resistivity profiles, are indicative of deeper section of unconsolidated sediments overlying the bedrock and are usually favourable locations for groundwater. An equiresistivity and water-level contour map based on well data is furnished, indicating the fresh water zone boundary deduced geophysically. Longitudinal velocities for the various rock types occurring in and around the area are tabulated for general interest. A bedrock map prepared on the basis of depths estimated geophysically is incorporated. The depths to bedrock computed from electrical and/or seismic data compare well with those obtained from borehole data.