A National Assessment of the Potential Linkage between Soil,and Surface and Groundwater Concentrations of Phosphorus

A meta‐analysis of three national databases determined the potential linkage between soil and surface and groundwater enrichment with phosphorus (P). Soil P was enriched especially under dairying commensurate with an increase in cow numbers and the tonnage of P‐fertilizers sold. Median P concentrations were enriched in surface waters receiving runoff from industrial and dairy land uses, and in groundwater beneath dairying especially in those aquifers with gravel or sand lithology, irrespective of groundwater redox status. After geographically pairing surface and groundwater sites to maximize the chance of connectivity, a subset of sites dominated by aquifers with gravel and sand lithology showed increasing P concentrations with as little as 10 years data. These data raise the possibility that groundwater could contribute much P to surface water if: there is good connectivity between surface and groundwater, intensive land use occurs on soils prone to leaching, and leached‐P is not attenuated through aquifers. While strategies are available to mitigate P loss from intensive farming systems in the short‐term, factors such as enriched soils and slow groundwater may mean that despite their use, there will be a long‐term input (viz. legacy), that may sustain surface water P enrichment. To avoid poor surface water quality, management and planning may need to consider the connectivity and characteristics of P in soil‐groundwater‐surface water systems.     

Groundwater risk assessment at a heavily industrialised catchment and the associated impacts on a peri-urban wetland

Industrial and agricultural activities often impose significant pressures to the groundwater quality and consequently degrade wetland ecosystems that depend mostly on subsurface water flow. Groundwater vulnerability and risk mapping is a widely used approach to assess the natural protection of aquifers and the associated pollution potential from human activities. In the particular study, the relatively new Pan-European methodology (COP method) has been applied in a highly industrialized peri-urban wetland catchment, located close to Athens city, to map the intrinsic vulnerability of the aquifer and evaluate the risk potential originating from local land uses. Groundwater analysis results for various parameters, including Phenols, PCBs and nutrients, have been used to validate the vulnerability and risk estimations while a biological assessment occurred to associate the mapping results with the wetland's ecological status. The results indicated that even though the natural protection of the aquifer is relatively high due to the dominant hydrogeologic and geomorphologic conditions, the groundwater pollution risk is considerable, mainly because of the existing hazardous land uses. The water quality of the groundwater accredited these findings and the ecological status of this peri-urban wetland also indicated significant impacts from industrial effluents.     

Artificial Groundwater Recharge Zones Mapping Using Remote Sensing and GIS: A Case Study in Indian Punjab

Artificial groundwater recharge plays a vital role in sustainable management of groundwater resources. The present study was carried out to identify the artificial groundwater recharge zones in Bist Doab basin of Indian Punjab using remote sensing and geographical information system (GIS) for augmenting groundwater resources. The study area has been facing severe water scarcity due to intensive agriculture for the past few years. The thematic layers considered in the present study are: geomorphology (2004), geology (2004), land use/land cover (2008), drainage density, slope, soil texture (2000), aquifer transmissivity, and specific yield. Different themes and related features were assigned proper weights based on their relative contribution to groundwater recharge. Normalized weights were computed using the Saaty’s analytic hierarchy process. Thematic layers were integrated in ArcGIS for delineation of artificial groundwater recharge zones. The recharge map thus obtained was divided into four zones (poor, moderate, good, and very good) based on their influence to groundwater recharge. Results indicate that 15, 18, 37, and 30 % of the study area falls under “poor,” “moderate,” “good,” and “very good” groundwater recharge zones, respectively. The highest recharge potential area is located towards western and parts of middle region because of high infiltration rates caused due to the distribution of flood plains, alluvial plain, and agricultural land. The least effective recharge potential is in the eastern and middle parts of the study area due to low infiltration rate. The results of the study can be used to formulate an efficient groundwater management plan for sustainable utilization of limited groundwater resources.     

Urbanization and its impact on groundwater: a remote sensing and GIS-based assessment approach

The perils of unplanned urbanization and increasing pressure of human activities on hydro-geomorphologic system often result in modification of the existing recharge mechanism, which leads to many environmental consequences. In the present research, an attempt has been made to investigate the applicability of remote sensing and geographical information system (GIS) in dealing with spatial and temporal variability of dynamic phenomena, like urbanization and its impact on groundwater. This paper covers primarily, quantitative and qualitative impacts of urban growth on the behavior of aquifer in Ajmer city (India). Urban growth of the Ajmer city in last 17 years has been estimated from the satellite images. Database related to urbanization and groundwater has been created in GIS. Groundwater recharge has been computed using a water balance approach known as Water Level Fluctuation Methodology. Recharge estimation methodology has been implemented in GIS to introduce the spatial variability of hydro-geological characteristics. Further, temporal and spatial variations in groundwater quality and quantity have been correlated with urban growth using overlay analysis in GIS. The study reveals a general decline in water table and quality with urbanization. Further, remote sensing and GIS technologies have been found useful in assessment of spatial and temporal phenomena of urbanization and its impact on groundwater system.     

高分辨率遥感影像在城市绿地信息提取中的应用研究

高分辨率卫星遥感图像数据量大、空间分辨率高、结构信息复杂、地物同物异谱现象更为突出等特征给专题信息提取技术带来了新的挑战。基于植被的光谱特征,利用监督分类、植被指数分类和目视解译等方法对QuickBird高分辨率卫星遥感影像的绿地信息进行提取,并对分类精度作了比对分析。研究结果表明,监督分类方法不能得到令人满意的结果,运用植被指数分类方法则有明显改善,其中归一化植被指数(NDVI)精度最高,因此NDVI能有效地对植被进行分类与识别。     

A SYSTEMS STUDY OF FUTURE GROUNDWATER DEVELOPMENT COSTS IN THE CHICAGO REGION1

The cost of developing groundwater resources in northeastern Illinois from 198cL2020 is estimated for the purpose of providing a basis for comparing alternative sources. Demands for each township in the study area are estimated at 10-year increments and are satisfied, where the supply is sufficient, in such a way as to minimize the cost subject to constraints on supply. Sources of water are two shallow aquifers with known potential yields and a series of deep aquifers treated as a single unit and modeled on a digital computer. For each township the costs of wells, pumps, power and rehabilitation is estimated for each aquifer on a per million gallons of water per day basis. In addition the cost of groundwater treatment necessary to raise the quality to that of treated Lake Michigan water is considered. Raw water costs are found to vary from 2 to 14 cents per 1000 gallons depending upon the depth to the deep aquifer water. Treated water costs vary from 22 to 53 cents per 1000 gallons, the lower costs applying to the largest users because of the economy of scale. It is found that with proper distribution of pumpage there is sufficient water in storage in the deep aquifers to meet groundwater demands through 2020.     

AN EXAMINATION OF THE MECHANISMS CONTROLLING GROUNDWATER GRADIENTS IN HYPER-ARID REGIONAL SEDIMENTARY BASINS1

ABSTRACT: Although evidence of modern recharge in the North African and Arabian sedimentary basin aquifers exists, it is difficult to determine the volume of recharge. Also, from the evidence of regional groundwater gradients, the flow within the aquifers seems to be appreciably greater than one would intuitively expect. A hypotehtical model embodying the characteristics of the aquifers has been used to investigate the likely significance of various possible flow mechanisms. It is shown that while dewatering in the unconfined area can possibly contribute to flows for a considerable period of time, the maintenance of water levels in the unconfined zone must be the result of modern recharge. It is also shown that recharge depths of less than 10 mm per annum are sufficient given suitable aquifer parameters. Results for various combinations of aquifer parameters and configurations are given, including layered aquifers and the effects of restricted oufflows. Comparisons are made using a “bench mark” example. The work indicates that there is little point in carrying out conventional hydrological balance studies in hyper-arid areas and that, instead, more emphasis should be placed upon good groundwater hydrographic data and modeling.     

GEOCHEMICAL INTERPRETATIONS OF GROUNDWATER FLOW SYSTEMS1

ABSTRACT. Interest in the geochemistry of groundwater is increasing owing to the great number of current projects involving underground liquid waste storage, artificial recharge of potable water, accidental contamination of groundwater bodies, sanitary landfills, and pollution monitoring. Geochemical techniques used to facilitate the understanding of a groundwater system range from extremely simple to those requiring sophisticated theories, equipment, and procedures. An interpretation of the simple trilinear diagram for samples collected from the Yucatan Peninsula of Mexico provided evidence that the fresh-water body was only a few tens of meters thick and was underlain everywhere by an extensive body of salt water. A geochemical technique that has been used effectively to identify the source of salt water in coastal aquifers is measurement of the carbon-14 concentrations. Carbon-14 has been used in a regional carbonate aquifer to determine the velocity of groundwater movement, rates of chemical reactions, and distribution of hydraulic conductivity. The application of principles of irreversible thermodynamics to groundwater systems provides a basis for constructing models which permit prediction, over both time and space, of changes in head distribution and chemical character of the water resulting from imposed stresses on the system. In essence, proper application of irreversible thermodynamics combines the potential theory of Hubbert with principles of reversible chemical thermodynamics, such as solution of carbonate minerals, to describe and explain controlling chemical reactions and processes of groundwater systems.     

POLLUTION SURVEILLANCE AND DATA ACQUISITION USING MULTISPECTRAL REMOTE SENSING1

Large scale water resource investigations and effective pollution surveillance programs require the development of additional instrumentation and techniques to supplement existing methods of data acquisition. As a result, interest is growing in the concept of remote sensing. Described in this paper is the multispectral sensor concept and its application in water resource studies.     

Proposed methodology to delineate bodies of groundwater according to the European water framework directive. Application in a pilot Mediterranean river basin (Málaga,Spain)

The term “body of groundwater” represents a new administrative tool established by the water framework directive (WFD) in order to manage European groundwaters. Its practical application raises some difficulties due to unclear definitions and the large heterogeneity of European aquifers. In this work, a methodology is proposed to carry out the delineation of bodies of groundwater according to the requirements of the WFD. This methodology faces up to some of the major difficulties that can arise during the delineation, such as the identification of bodies of groundwater in multilayered aquifers, boundaries between superposed groundwater bodies, and delimitation in low permeability materials or in dismembered aquifers. In order to show its practical application, the proposed methodology is applied in a pilot Mediterranean river basin located in southern Spain. Results show that previous knowledge of the hydrogeological conditions is necessary to enable a correct delineation of groundwater bodies. Finally, alternative procedures are proposed for low permeability and small aquifers in order to reduce the number of groundwater bodies identified and simplify their overall management.     

Effects of climate and land use changes on groundwater resources in coastal aquifers

To estimate the freshwater loss in coastal aquifers due to salinisation, a numerical model based on the sharp interface assumption has been introduced. The developed methodology will be useful in areas where limited hydrological data are available. This model will elaborate on the changes in fresh groundwater loss with respect to climate change, land use pattern and hydrologic soil condition. The aridity index has been introduced to represent the variations in precipitation and temperature. The interesting finding is that the deforestation leads to increase groundwater recharge in arid areas, because deforestation leads to reduce evapotranspiration even though it favors runoff. The combined climate and land use scenarios show that when the aridity index is less than 60, the agricultural lands give higher groundwater recharge than other land use patterns for all hydrologic soil conditions. The calculated recharge was then used to estimate the freshwater-saltwater interface and percentage of freshwater loss due to salinity intrusion. We found that in arid areas, the fresh groundwater loss increases as the percentage of forest cover increases. The combined effects of deforestation and aridity index on fresh groundwater loss show that deforestation causes an increase in the recharge and existing fresh groundwater resource in areas having low precipitation and high temperature (arid climates).     

Conjunctive Water Use in Confined Basalt Aquifers: An Evaluation Using Geochemistry,a Numerical Model,and Historical Water Level

As withdrawals from deep compartmentalized aquifers increasingly exceed recharge throughout the western United States, conjunctive water use management alternatives have become an applied research priority. This study highlights both details and limitations of the role of irrigation canal seepage as groundwater recharge, revealing the regional limitations of canal seepage as a dependable source of recharge in overdrawn aquifers. A suite of geochemical indicators were used together with a numerical model to evaluate current and future management scenarios focused on recharge derived from seepage from a region‐wide irrigation canal system. Twenty‐five years of static groundwater level data were used to relate spatial trends determined using geochemistry and groundwater modeling with “on‐the‐ground” management practices, which vary based on acreage, crop, and irrigation scheduling. Increasing groundwater age determined using isotope analysis, and declines in potentiometric heads, each correlate with increasing distance from the canal reaches. Predictive modeling indicates that if pumping is gradually reduced, as has been suggested by management agencies, that recharge from canal seepage will be negligible by 2035 due to regional groundwater through‐flow and the pattern of potentiometric head recovery. Unfortunately, historic hydrographs suggest that under current groundwater development conditions most wells are not sustainable, irrespective of proximity to the canal.     

ESTIMATING EVAPORATION FROM UTAH'S GREAT SALT LAKE USING THERMAL INFRARED SATELLITE IMAGERY1

ABSTRACT: Water surface temperatures can be obtained from satellite thermal remote sensing. Landsat and other satellites sense emitted thermal infrared radiation on a regular basis over much of the earth's surface. Evaporation is accomplished by the net transport of mass from the water surface to the atmosphere. The evaporative transfer predominantly determines the water surface temperature. Hence, there should be good correlations between evaporation and surface temperatures. Previous investigations on Utah Lake with satellite-derived temperatures and pan- and model-derived evaporation values have produced good correlations. However, more study was required with additional satellite data and evaporation measurements for saltwater conditions. The applicability of this method for estimating evaporation on Utah's Great Salt Lake was of particular interest at this time because of the unprecedented rise of this terminal lake. Satellite thermal data and evaporation data from four different years were obtained for the Great Salt Lake and the surrounding region. More than 350 correlation and linear regression analyses were performed on the temperature and evaporation data. The lake salt concentrations were also factored into the analyses in several different ways. The correlation results were generally very good and a methodology for using satellite-derived water surface temperatures along with salt concentrations was developed to estimate evaporation.     

Multiwell Technique of Saline and Nonsaline Groundwater Pumping from Coastal Aquifers

In this article, the authors explore their recent study, which introduces the concept of extracting saline water and fresh water simultaneously from groundwater aquifers to produce water that is suitable for irrigation. To achieve these results, multiwell modeling concepts are used to exploit both the saline and nonsaline aquifer domains from geologic formations where a freshwater aquifer domain is either underlain or overlain by a saline aquifer domain. The water from these domains are either mixed to an acceptable salinity level after independent withdrawal from separate, saline or nonsaline domains present within the same aquifer, or mixed from the domains to achieve acceptable levels of salinity before withdrawal.     

水面实测遥感光谱数据的叶绿素a反演模型构建—以太湖为例

叶绿素a遥感反演的关键是建立遥感数据和叶绿素含量的定量关系。本文根据2007年11月在太湖实测的水体反射光谱及实验室分析得到的叶绿素浓度数据，对太湖水体反射光谱特征与叶绿素浓度之间的关系进行分析和建模。研究结果表明：687nm附近反射峰位置对叶绿素浓度有很好的指示作用，在太湖水体叶绿素浓度的估测模型中，反射峰位置的指数模型要优于线性模型；叶绿素a浓度与684nm和633nm附近的一阶微分有很好的相关性，利用R’684和R’633所建叶绿素a浓度反演模型的估算精度R2分别达到0.89和0.91。     

Combination of multispectral remote sensing, variable rate technology and environmental modeling for citrus pest management

The Lower Rio Grande Valley (LRGV) of south Texas is an agriculturally rich area supporting intensive production of vegetables, fruits, grain sorghum, and cotton. Modern agricultural practices involve the combined use of irrigation with the application of large amounts of agrochemicals to maximize crop yields. Intensive agricultural activities in past decades might have caused potential contamination of soil, surface water, and groundwater due to leaching of pesticides in the vadose zone. In an effort to promote precision farming in citrus production, this paper aims at developing an airborne multispectral technique for identifying tree health problems in a citrus grove that can be combined with variable rate technology (VRT) for required pesticide application and environmental modeling for assessment of pollution prevention. An unsupervised linear unmixing method was applied to classify the image for the grove and quantify the symptom severity for appropriate infection control. The PRZM-3 model was used to estimate environmental impacts that contribute to nonpoint source pollution with and without the use of multispectral remote sensing and VRT. Research findings using site-specific environmental assessment clearly indicate that combination of remote sensing and VRT may result in benefit to the environment by reducing the nonpoint source pollution by 92.15%. Overall, this study demonstrates the potential of precision farming for citrus production in the nexus of industrial ecology and agricultural sustainability.     

Determination of groundwater potential in obiaruku and environs using surface geoelectric sounding

The interpretation of ten resistivity curves in Obiaruku and environs indicates that the area has a great groundwater potential. Correlation of the curves with the lithologic log from a nearby borehole in Ghana quarters, reveals the lithologic succession as an extensive sandy unit between the range of 20 m and 136 m. The medium grained sand unit, which is the aquiferous zone, has a resistivity range of between 300 Ω m and 600 Ω m. The result of the interpreted data and the lithologic log from the borehole indicates three to five geoelectric layers except at Adonishaka, which has a confined aquifer in the third layer and Umukwata that has a confined aquifer in the second layer, the study area generally has an unconfined aquifer, which is in the second layer. In the event of pollution, the groundwater may be contaminated. Sinking of water borehole is not recommended in these areas. Boreholes for potable water are therefore recommended at locations within Adonishaka and Umukwata areas. The present study acts as a guide for future groundwater exploration and exploitation.     

A Stochastic Modeling Approach to Address Hydrogeologic Uncertainties in Modeling Wellhead Protection Boundaries in Karst Aquifers1

Abstract: Development of any numerical ground‐water model is dependent on hydrogeologic data describing the subsurface. These data are obtained from geologic core analyses, stratigraphic analyses, aquifer performance tests, and geophysical studies. But typically in remote areas, these types of data are very sparse and site‐specific in terms of the aerial extent of the resource to be modeled. Uncertainties exist as to how well the available data from a few locations defines a heterogeneous surficial aquifer such as the Biscayne Aquifer in Miami‐Dade County, Florida. This is particularly the case when an exceptionally conductive horizontal flow zone is detected at one site due to specialized testing that was not historically conducted at the other at sites that provided data for the model. Not adequately accounting for the potential effect of the high flow zone in the aquifer within a ground‐water numerical model, even though the zone may be of very limited thickness, might underpredict the well field protection capture boundaries. Applied Stochastic ground‐water modeling in determining well field protection zones is steadily becoming important in addressing the uncertainty of the hydrogeologic subsurface parameters, specifically in karstic heterogeneous aquifers. This is particularly important in addressing the uncertainty of a 60‐day travel time capture zone in the Northwest Well Field, Miami‐Dade County, where a predominantly high flow zone controls much of the flow in the production wells. A stochastic ground‐water modeling application along with combination of pilot points and regularization technique is presented to further consolidate the uncertainty of the subsurface.     

Sensitivity of Thermal Habitat of a Trout Stream to Potential Climate Change,Wisconsin, United States1

Abstract: Airborne thermal remote sensing from four flights on a single day from a single‐engine airplane was used to collect thermal infrared data of a 10.47‐km reach of the upper East Branch Pecatonica River in southwest Wisconsin. The study uses a one‐dimensional stream temperature model calibrated with the longitudinal profiles of stream temperature created from the four thermal imaging flights and validated with three days of continuous stream temperature data from instream data loggers on the days surrounding the thermal remote‐sensing campaign. Model simulations were used to quantify the sensitivity of stream thermal habitat to increases in air and groundwater temperature and changes in base flow. The simulations indicate that stream temperatures may reach critical maximum thresholds for brook trout (Salvelinus fontinalis) and brown trout (Salmo trutta) mortality, particularly if both air temperature increases and base flow declines. The approach demonstrates that thermal infrared data can greatly assist stream temperature model validation due to its high spatial resolution, and that this spatially continuous stream temperature data can be used to pinpoint spatial heterogeneity in groundwater inflow to streams. With this spatially distributed data on thermal heterogeneity and base‐flow accretion, stream temperature models considering various climate change scenarios are able to identify thermal refugia that will be critical for fisheries management under a changing climate.     

Remote Sensing and GIS Techniques for Selecting a Sustainable Scenario for Lake Koronia,Greece

During recent decades, Lake Koronia has undergone severe degradation as a result of human activities around the lake and throughout the basin. Surface and groundwater abstraction and pollution from agricultural, industrial, and municipal sources are the major sources of degradation. Planning a restoration project was hampered by lack of sufficient data, with gaps evident in both spatial and temporal dimensions. This study emphasized various remote sensing and geographic information system techniques, such as digital image processing and geographic overlay, to fill gaps using satellite imagery and other spatial environmental, hydrological, and hydrogeological data in the process of planning the restoration of Lake Koronia, following Ramsar guidelines. Current and historical remote sensing data were used to assess the current status and level of degradation, set constraints and define the ideotype for the restoration, and, finally, define and select the best restoration scenario.