Nutrient chemistry of groundwater in an intensively irrigated region of southern India

The concentration of nutrients in groundwater acts as an indicator to identify the influence of agricultural activities on the shallow subsurface environment. Hence, the present study was carried out to assess nutrient concentration (nitrate, phosphate and potassium) and understand its spatial and seasonal variations in the groundwater of Palar and Cheyyar River basin, Tamil Nadu, India. The groundwater samples collected from 43 wells were analyzed for nutrients once a month from January 1998 to June 1999. Results of the study suggested that agricultural activities, including application of fertilizers, soil mineralization processes and irrigation return flow, are major processes regulating the nutrients chemistry in the groundwater of this region. Groundwater in the sedimentary formation has comparatively higher concentration of nutrients than the groundwater in hard rock formations, which seems to be due to the adsorption of nutrients by the weathered rock materials. The seasonal water level fluctuation shows that rising water level increases nutrients concentration in groundwater due to the agriculture related activities. The results also indicate that nitrate and potassium concentrations are within the recommended drinking water limits, whereas phosphate concentration exceeds its drinking water limit and 35% of the samples are unsuitable for drinking purposes.Electronic Supplementary Material Supplementary material is available for this article at     

Determination of groundwater availability in shallow arid region aquifers utilizing GIS technology: a case study in Hada Al-Sham, Western Saudi Arabia

A simple, physically based method is developed in this paper to assist in the allocation of areas with high groundwater potential and for the determination of maximum allowed pumping rate to ensure proper groundwater management. This method utilizes the aquifer physical properties as well as GIS technology to accomplish this purpose. The design of this method was considered to be applicable in areas with little data, such as in most arid regions. This technique was applied to a catchment in an arid environment where qualitative as well as quantitative analyses of the results were undertaken. Locations of available groundwater and rates of maximum allowable pumping were compared with observations and experiments in the field and a good agreement was found. It was concluded that the best groundwater location was in the alluvial area, which represents only 16% of the total aquifer, which is a typical case in arid region catchments. The rate of maximum pumping was estimated to be 65 m³/h. However, to benefit 55% of the area, the maximum pumping rate should only be 40 m³/h with an average rate throughout the area (55%) of about 24 m³/h.This revised version was published online in December 2004 with corrections to the category.     

Using CRD method for quantification of groundwater recharge in the Gaza Strip, Palestine

Rainfall is the main source of groundwater recharge in the Gaza Strip area in Palestine. The area is located in the semi-arid zone and there is no source of recharge other than rainfall. Estimation of groundwater recharge from rainfall is not an easy task since it depends on many uncertain parameters. The cumulative rainfall departure (CRD) method, which depends on the water balance principle, was used in this study to estimate the net groundwater recharge from rainfall. This method does not require much data as is the case with other classical recharge estimation methods. The CRD method was carried out using optimisation approach to minimise the root mean square error (RMSE) between the measured and the simulated groundwater head. The results of this method were compared with the results of other recharge estimation methods from literature. It was found that the results of the CRD method are very close to the results of the other methods, but with less data requirements and greater ease of application. Based on the CRD method, the annual amount of groundwater recharge from rainfall in the Gaza Strip is about 43 million m³. An erratum to this article can be found at     

Hydrochemical characteristics and salinity of groundwater in the Ejina Basin, Northwestern China

A hydrochemical investigation was conducted in the Ejina Basin to identify the hydrochemical characteristics and the salinity of groundwater. The results indicate that groundwater in the area is brackish and are significantly zonation in salinity and water types from the recharge area to the discharge area. The ionic ration plot and saturation index (SI) calculation suggest that the silicate rock weathering and evaporation deposition are the dominant processes that determine the major ionic composition in the study area. Most of the stable isotope δ¹⁸O and δD compositions in the groundwater is a meteoric water feature, indicating that the groundwater mainly sources from meteoric water and most groundwater undergoes a long history of evaporation. Based on radioactive isotope tritium (³H) analysis, the groundwater ages were approximately estimated in different aquifers. The groundwater age ranges from less than 5 years, between 5 years and 50 years, and more than 50 years. Within 1 km of the river water influence zone, the groundwater recharges from recent Heihe river water and the groundwater age is about less than 5 years in shallow aquifer. From 1 km to 10 km of the river water influence zone, the groundwater sources from the mixture waters and the groundwater age is between 5 years and 50 years in shallow aquifer. The groundwater age is more than 50 years in deep confined aquifer.     

Use of mineral/solution equilibrium calculations to assess the potential for carnotite precipitation from groundwater in the Texas Panhandle,USA

This study investigated the potential for the uranium mineral carnotite (K₂(UO₂)₂(VO₄)₂·3H₂O) to precipitate from evaporating groundwater in the Texas Panhandle region of the United States. The evolution of groundwater chemistry during evaporation was modeled with the USGS geochemical code PHREEQC using water-quality data from 100 groundwater wells downloaded from the USGS National Water Information System (NWIS) database. While most modeled groundwater compositions precipitated calcite upon evaporation, not all groundwater became saturated with respect to carnotite with the system open to CO₂. Thus, the formation of calcite is not a necessary condition for carnotite to form. Rather, the determining factor in achieving carnotite saturation was the evolution of groundwater chemistry during evaporation following calcite precipitation. Modeling in this study showed that if the initial major-ion groundwater composition was dominated by calcium-magnesium-sulfate (>70 precent Ca + Mg and >50 percent SO₄ + Cl) or calcium-magnesium-bicarbonate (>70 percent Ca + Mg and <70 percent HCO₃ + CO₃) and following the precipitation of calcite, the concentration of calcium was greater than the carbonate alkalinity (2mCa⁺² > mHCO₃⁻ + 2mCO₃⁻²) carnotite saturation was achieved. If, however, the initial major-ion groundwater composition is sodium-bicarbonate (varying amounts of Na, 40–100 percent Na), calcium-sodium-sulfate, or calcium-magnesium-bicarbonate composition (>70 percent HCO₃ + CO₃) and following the precipitation of calcite, the concentration of calcium was less than the carbonate alkalinity (2mCa⁺² < mHCO₃^- + 2mCO₃⁻²) carnotite saturation was not achieved. In systems open to CO_2, carnotite saturation occurred in most samples in evaporation amounts ranging from 95 percent to 99 percent with the partial pressure of CO₂ ranging from 10^−3.5 to 10^−2.5 atm. Carnotite saturation occurred in a few samples in evaporation amounts ranging from 98 percent to 99 percent with the partial pressure of CO₂ equal to 10^−2.0 atm. Carnotite saturation did not occur in any groundwater with the system closed to CO₂.     

北方某经济开发区地下水污染调查评价

本文应用污染指数法,对北方某经济开发区及周边地下水水质进行了污染评价,结果表明研究区地下水水质以轻污染和中污染为主,局部地区出现较重污染,主要指标为硝酸盐氮、三氯甲烷和三氯乙烯。通过对工业废水、再生水、河水水质的检测,发现研究区地表水水质与污水处理厂再生水排放密切相关,地下水污染很可能与开发区企业排污有关。由于开发区所处位置的环境敏感性和脆弱性,建议今后在开发区及附近继续开展相关研究,进一步查明地下水的硝酸盐氮及有机污染物来源、污染途径,建立完善的监测体系,以便及时切断污染源,保障城市及当地供水安全。