GIS-based assessment of non-equilibrium pattern between groundwater recharge and irrigation draft in a semi-arid region of Rajasthan,India

Over-exploitation of groundwater for irrigation can result in drastic reduction in groundwater level in Jodhpur district of western Rajasthan, India. In this study, we used the long-term trend analysis of seasonal groundwater level data to predict the future groundwater scenario in 33 villages of Jodhpur district, assessed the impact of water harvesting structures on groundwater recharge and explored the non-equilibrium between groundwater recharge and irrigation draft in the study area. Analysis of groundwater level data from 26 observation wells in 33 villages in the pre-monsoon period showed that groundwater level decreased continuously at the rate of 2.07 m/a. With this declining rate, most of the tube wells(including the well with the maximum depth of 193 m) are predicted to become completely dry by 2050. Behavior of temporal groundwater level data in the study period(from 2004 to 2012) can be explained by different geospatial maps, prepared using Arc GIS software. Statistical analysis of the interpolated maps showed that the area with the maximum positive groundwater recharge occupied 63.14% of the total area during 2010–2011 and the area with the maximum irrigation draft accounted for 56.21% of the total area during 2011–2012. Higher groundwater recharge is attributed to the increase in rainfall and the better aquifer condition. Spatial distribution for the changes of average groundwater recharge and draft(2008–2009 and 2011–2012) showed that 68.50% recharge area was in positive change and 45.75% draft area was in negative change. It was observed that the area of the irrigation draft exceeded that of the groundwater recharge in most of the years. In spite of the construction of several shallow water harvesting structures in 2009–2010, sandstone aquifer zones showed meager impact on groundwater recharge. The best-fit line for the deviation between average groundwater fluctuation due to recharge and irrigation draft with time can be represented by the polynomial curve. Thus, over-exploitation of groundwater for agricultural crops has result in non-equilibrium between groundwater recharge and irrigation draft.     

华北平原中部深层含水层水文地质参数研究

以华北平原中部第四系深层含水层为研究对象,通过分析其水文地质条件及抽水试验数据资料,选取水位恢复数据序列进行求参计算.在对一般简化算法进行改进的基础上,提出tp值的确定及其对计算结果的影响,继而介绍更为简便可靠的Cooper-Jacob算法作为目标含水层水文地质参数的最优计算方法.     

塔克拉玛干沙漠浅层地下水位对单井抽水的响应过程研究

为了研究人工抽水行为对周边地下水位的影响,在塔里木沙漠公路防护林生态工程第69号水源井处布设了抽水试验观测场,利用连续定位观测数据,分析了地下水位降深与时间的关系、地下水位的空间差异性规律;在此基础上利用Neuman井流模型方法,分析了含水层的传导性和贮水性,确定了该区域的相关水文地质参数;并利用Theis预报方法,对抽水引起的水位变化进行了短期预报。研究结果表明:抽水过程水位上升和下降过程均可分为快速和慢速两个阶段,含水层具有弹性释水和重力释水作用的特征;计算得出部分水文地质参数为:T=1.50E+1m3/d,Kh=3.74E+1 m/d,σ=1.12E-2;预测得出持续抽水1000 min时的抽水影响半径约为400m。文中研究所得出的水文地质参数符合该地区的水文地质条件,可作为相似区域水文地质学研究的参考;地下水位在抽水行为结束后,能够恢复到抽水前的水平;抽水行为对周边地下水位的影响范围不大,多个水源井之间不会形成相互干扰,不会引起天然地下水位的持续下降。研究结果可为沙漠公路沿线地下水资源的可持续利用和防护林生态工程整体的稳定性及长久运行提供一定的理论依据。     

黄河三角洲水盐演化及补给来源 ——基于水化学与同位素分析

对河口地区地表水和浅层地下水采样调查,结合离子全组分和稳定同位素证据,分析了研究区水化学特征与各水体补给来源,探讨了长期引黄灌溉对区域水循环、地表水-地下水交换的影响。结果显示：(1)河口区地表水与浅层地下水都具有较高的矿化度,浅层地下水与地表水平均矿化度分别为27.96、23.17 g·L-1,地表水和浅层地下水中阳离子Mg²⁺、Na⁺、K⁺,阴离子Cl^-、SO^2-₄是与总溶解固体(TDS)显著相关的主要离子成分;(2)浅层地下水水化学类型为Cl-Na·K,是典型的海水混合或者卤水;地表水由于工、农业和城市污染,水化学类型向Cl·SO₄-Na·K·Ca变化,水化学类型变化复杂;(3) 地表水水体的盐分补给来源于海水混合以及城市及农业污染,而浅层地下水的输入则来自海水入侵以及降水、地表水的下渗补给;(4) 生态调水后地表水对浅层地下水的补给高值区主要分布在农田和近海湿地,补给比例48%~81%,而海岸滩涂带地下水的补给比例最低,这可能与海岸含水层渗透系数相对农田和湿地较小有关。     

鄂尔多斯高原内流区地下水开发利用方式研究

针对鄂尔多斯高原内流区地下水资源可持续开发利用问题,建立了理想数值模型。在此模型基础上,采用控制性数值试验方法、定量与定性分析相结合的方法,通过典型内流区稳定流分析、无第四系内流区稳定流分析、参数灵敏度分析,对该区内地下水资源开发利用中的井位、过滤器顶部埋深、过滤器合理长度、开采目的层等关键技术问题进行了分析。结果表明,在该区内地下水资源合理开发利用方式应为：采用中段悬挂式过滤器的非完整井,在远离湖泊的位置,单一开采白垩系含水层地下水。同时指出,控制性数值试验方法、定量与定性分析相结合的方法,在地下水资源可持续开发利用中,乃至地下水科学领域,是值得重视和进一步发展的研究方法。     

Degradation and sorption of atrazine, hexazinone and procymidone in coastal sand aquifer media

The degradation, sorption and transport of atrazine, hexazinone and procymidone in saturated coastal sand aquifer media were investigated in batch and column experiments. The pesticides were incubated with sterilised and non-sterilised groundwater or a mixture of groundwater and the aquifer material in the dark at 15 degrees C for 120 days. The estimated half-lives of the pesticides (and their ranges) in the mixture of groundwater and aquifer sand were 36 (31-40), 54 (40-77) and 84 (46-260) days for atrazine, procymidone and hexazinone, respectively. Compared with the relevant results for the groundwater-sand mixture phase, the estimated half-life of pesticides in the groundwater phase alone was shorter for procymidone (21 days) but longer for hexazinone (134 days); atrazine was not degraded in the groundwater phase. Chemical degradation appeared to have played the predominant role in the degradation of hexazinone and procymidone in the aquifer system, while both chemical and biological processes seemed to be important for the degradation of atrazine. Batch isothermal experiments were carried out at pH 4.6-4.7 to obtain sorption coefficients under equilibrium conditions. The isothermal data of the pesticides fitted well with the non-linear Freundlich function with an exponent of sorption coefficient that was greater than one. Contrary to reports in the literature, sorption of atrazine was the greatest, and procymidone was slightly more sorbed than hexazinone. A column experiment was conducted at a typical field-flow velocity of 0.5 m day(-1) over 60 days to study pesticide attenuation and transport in flow dynamic conditions. Retardation factors, R, derived from a two-site sorption/desorption model were 8.22, 1.76 and 1.63 for atrazine, procymidone and hexazinone, respectively. Atrazine displayed the lowest mobility and the mobility of procymidone was only slightly less than that of hexazinone, which is consistent with observations in the batch experiment. A possible explanation for these observations is that ionic atrazine is bound to oppositely charged ionic oxides, and ionic oxides have less effect on the sorption of the non-ionic procymidone. The significant tailing in the pesticide breakthrough curves (BTCs) in comparison with the bromide BTC, together with model-simulated results, suggests that the transport of the pesticides was under chemical non-equilibrium conditions with R values that were less than their equivalent values predicted using the batch equilibrium isothermal data. As a result of non-linear kinetic sorption, retardation factors of the pesticides in groundwater systems would not be constant and will decrease with decreasing pesticide concentrations and increasing flow velocities. Hence, the use of equilibrium isotherm data will probably over-predict the sorption of pesticides in groundwater systems. Rhodamine WT, a commonly used groundwater tracer, was significantly retarded (R = 5.48) and its BTC was much more spread out than the bromide BTC. Therefore, it would not be a good tracer for the indication of groundwater flow velocity and dispersion for the coastal sand aquifer system. In contrast to some aquifer media, the dye tracer was unsuitable as a marker of the appearance of atrazine in a coastal sand aquifer system.     

鄂尔多斯高原外流区地下水开发利用方式研究

针对鄂尔多斯高原外流区地下水资源可持续开发利用问题,建立了理想数值模型.采用控制性数值试验方法以及定性与定量分析相结合的方法,通过典型稳定流分析、无第四系稳定流分析、参数灵敏度分析,对在鄂尔多斯沙漠高原外流区开采地下水资源中的井位、过滤器顶部埋深、过滤器合理长度、开采目的层等关键技术问题进行了分析研究,研究结果表明,在鄂尔多斯沙漠高原外流区宜采用中段悬挂式非完整井远离河流单一开采白垩系含水层地下水,同时指出控制性数值试验方法以及定量分析定性分析相结合的方法,在地下水资源可持续开发利用乃至地下水科学领域,是值得重视和进一步发展的研究方法.     

锡林河流域地下水位管理阈值研究

地下水资源是维系锡林河流域社会经济发展和生态环境稳定的关键因子。立足于地下水位这一关键性指标,采用地下水可持续性评价和数值模拟模型相结合的方法,探讨地下水安全利用方式。结果表明:现状年河谷平原的地下水可持续性较强,而开采集中的城市规划区及毛登牧场可持续性一般或较差;丰沛的降水及富水性较强的含水层增强了地下水资源可持续性,但农牧业快速发展和农灌集中开采,破坏了城市规划区周边及毛登牧场的地下水均衡关系,通过设置和对比不同开采方案,限制灌溉规模成为未来解决这一危机的首要途径,即2020年应减少903.23×104m3开采量,其管理地下水位阈值为0.13~0.55 m。     

Source identification of nitrate in the upper aquifer system of the Wadi Shueib catchment area in Jordan based on stable isotope composition

Groundwater forms the main freshwater supply in arid and semi-arid areas,and contamination of this precious resource is complicated by the slow rate of recharge in these areas.Nitrate contamination of groundwater is a global water quality problem,as it entails threat to human health as well as aquatic ecosystems.Source identification of contamination is the cornerstone and a prerequisite for any effective management program of water quality.Stable isotope composition of the dissolved nitrate(δ¹⁵N-NO₃-andδ¹⁸O-NO₃-)has been applied to identify NO₃-sources and the main transformation processes in the upper aquifer system(A1/2,A4,and B2/A7 aquifers)in the Wadi Shueib catchment area,Jordan.Moreover,the stable isotope compositions of the groundwater(δ²H-H₂O andδ¹⁸O-H₂O)in conjunction with the groundwater hydrochemistry were integrated to investigate the origin and evolution of the groundwater.Results revealed that groundwater in the study area is fresh and hard-very hard water,and mainly a Ca-Mg-Cl type.NO₃-concentration was in the range of 7.0-74.0 mg/L with an average of 37.0 mg/L.Most of the samples showed concentration higher than the natural background concentration of NO₃-(5.0-10.0 mg/L).Theδ²H-H₂O andδ¹⁸O-H₂O values indicated that the groundwater is meteoric,and of Mediterranean origin,with a strong evaporation effect.Theδ¹⁵N-NO₃-values ranged between 6.0‰and 11.3‰with an average of 8.7‰,and theδ¹⁸O-NO₃-values ranged between 1.6‰and 5.9‰with an average of 3.4‰.These values are in conformity with the stable isotope composition of nitrate derived the nitrification of wastewater/manure,and soil NH4.Nitrification and denitrification are the main transformation processes affecting nitrogen species.Statistical analysis revealed no significant differences in theδ²H-H₂O andδ¹⁸OH₂O values,andδ¹⁵N-NO₃-andδ¹⁸O-NO₃-values for the three aquifers(A1/2,A4,and B2/A7),indicating that the groundwater of these aquifers has the same origin,and a common source of pollution.     

A field tracer study of attenuation of atrazine,hexazinone and procymidone in a pumice sand aquifer

A field tracer experiment, simulating point source contamination, was conducted to investigate attenuation and transport of atrazine, hexazinone and procymidone in a volcanic pumice sand aquifer. Preliminary laboratory incubation tests were also carried out to determine degradation rates. Field transport of the pesticides was observed to be significant under non‐equilibrium conditions. Therefore, a two‐region/two‐site non‐equilibrium transport model, N3DADE, was used for analysis of the field data. A lump reduction rate constant was used in this paper to encompass all the irreversible reduction processes (eg degradation, irreversible adsorption, complexation and filtration for the pesticides adsorbed into particles and colloids) which are assumed to follow a first‐order rate law. Results from the field experiment suggest that (a) hexazinone was the most mobile (retardation factor R = 1.4) and underwent least mass reduction; (b) procymidone was the least mobile (R = 9.26) and underwent the greatest mass reduction; (c) the mobility of atrazine (R = 4.45) was similar to that of rhodamine WT (R = 4.10). Hence, rhodamine WT can be used to delimit the appearance of atrazine in pumice sand groundwater. Results from the incubation tests suggest that (a) hexazinone was degraded only in the mixture of groundwater and aquifer material (degradation rate constant = 4.36 × 10^?3 day^?1); (b) procymidone was degraded not only in the mixture of groundwater and aquifer material (rate constant = 1.12 × 10^?2 day^?1) but also in the groundwater alone (rate constant = 2.79 × 10^?2 day^?1); (c) atrazine was not degraded over 57 days incubation in either the mixture of aquifer material and groundwater or the groundwater alone. Degradation rates measured in the batch tests were much lower than the total reduction rates. This suggests that not only degradation but also other irreversible processes are important in attenuating pesticides under field conditions. Hence, the use of laboratory‐determined degradation rates could underestimate reduction of pesticides in field conditions. © 2001 Society of Chemical Industry     

石羊河流域的水化学特征及其地表水与地下水的相互转化

通过分析石羊河流域地表水与地下水的水化学特征,可以了解石羊河流域地表水与地下水的相互转化关系。研究结果表明:(1)武威盆地,在山前地带,出山河水入渗转化为地下水;溢出带地下水以泉的形式转化为地表水;进入细土平原后,河水又补给地下水;在农灌区引河水又通过田间入渗反补地下水。(2)民勤盆地,地下水主要通过引水灌溉和河水补给。     

准噶尔盆地西北缘新垦绿洲地下水动态

根据观测井地下水实测数据,对位于准噶尔盆地西北缘的克拉玛依农业综合开发区地下水埋深时空变化及其驱动因素进行分析。结果表明：①1997-2009年,该区地下水位呈持续上升趋势,农业综合开发区地下水位上升与灌溉期有着直接的关系;②空间分布呈现沿开发区主干道（蓝天大道）两翼,地下水位向西北缘和东北缘逐渐抬升,形成水位抬升中心...     

Dynamics of groundwater recharge near a semi-arid Mediterranean intermittent stream under wet and normal climate conditions

In arid and semi-arid stream-dominated systems, the temporal variability in groundwater recharge has not been widely addressed. Various questions remain about the sources of groundwater recharge, its patterns, and the appropriate measuring techniques. Hence, the main objective of the present study was to assess the changes that might affect the pattern of groundwater recharge under wetter than normal surface water availability. Therefore, the groundwater depth was monitored near a semi-arid Mediterranean intermittent stream on the piedmont of the High Atlas Mountains in the mountain catchment of the Wadi Rheraya over two hydrological years (2014-2016) with different climate conditions: extreme wet and normal conditions. Groundwater recharge was assessed using the episodic master recession algorithm. During the two years, the pattern of groundwater recharge was dominated by episodic events and by a high seasonality from wet seasons to dry seasons. In the wet year (2014-2015), the highest groundwater recharge was recorded following an extreme flood, which deeply replenished groundwater. Furthermore, an exceptional steady state of the groundwater depth was induced by a steady groundwater recharge rate. For several groundwater recharge events, the assessed recharge had multiple sources, mainly from streamflow at the local scale, but possibly from precipitation, underflow, deep percolation or irrigation return from the upstream part of the catchment. Local recharge by streamflow was likely to be short-lived, and lateral recharge was likely to last longer. Consequently, the episodic master recession algorithm estimated the total groundwater recharge that could encompass various sources. In the future, more studies and multidisciplinary approaches should be carried out to partition these sources and determine their specific contributions. In semi-arid stream-dominated systems, different groundwater recharge patterns induced by extreme hydrological events (e.g., wet events) and various potential sources of groundwater recharge should be considered when assessing and predicting groundwater recharge.     

河谷区地下水人工回灌试验研究

河谷区采用现场坑灌和井灌试验,通过测定回灌量衰减和渗透系数的变化来分析回灌效果.坑灌回灌量中期衰减24%,后期衰减40%,在整个回灌过程中区域水位上升1.1～1.3 m,实际形成水丘规模很小,反映出试验层水平渗透能力强.井灌初期回灌量衰减33%,在后期基本稳定,但总趋势仍在衰减,含水层渗透系数以主孔为中心,由远到近渗透...     

The ability of indigenous micro-organisms to degrade isoproturon, atrazine and mecoprop within aerobic UK aquifer systems

The potential for the herbicides isoproturon, atrazine and mecoprop to degrade in the major UK aquifers of chalk, sandstone and limestone was studied using laboratory microcosms spiked at 100 microg litre(-1). Significant mecoprop degradation was only observed in sandstone groundwater samples. Atrazine transformation, based on the formation of metabolites, did occur in most groundwater samples, but only at a rate of 1-3% per year. A potential to degrade isoproturon was observed in groundwater samples from each of the aquifer types, with the most rapid and consistent degradation occurring at the sandstone field site. Biodegradation was confirmed by the formation of monodesmethyl- and didesmethyl-isoproturon. Isoproturon degradation potential rates obtained from the groundwater microcosms could not be correlated with either dissolved organic carbon or numbers of bacteria in the groundwater. It was noted that the ability of the groundwater at a field site to degrade a pesticide was not related to performance of the soil above.     

华北平原地下水资源功能衰退与恢复途径研究

相对20世纪50年代末,至本世纪华北平原地下水总开采量由不足100×108m3/a增至211.98×108m3/a,超出地下水可利用资源量192.31×108m3/a。长期超量开采和不合理的开采布局,使地下水水位持续下降、含水层疏干体积不断增加,地下水位降落漏斗持续扩展,地下水的资源功能不断衰退的同时产生地面沉降、地面塌陷、咸水入侵等环境地质问题。采取农业节水、工业调整开采强度布局、建立应急用水机制、地表水与地下水联合调蓄、本地劣质水资源化等综合举措,修复和涵养华北平原地下水系统势在必行。     

Rate of transformation of atrazine and bentazone in water-saturated sandy subsoils

When pesticides leach through the soil to the upper groundwater zone, it is important to know whether further transformation occurs before the pumping wells for drinking water are reached. Atrazine and bentazone were incubated (at 10°C) in five water-saturated sandy subsoils (collected at depths between 1·5 and 3·5 m), simulating the conditions in the field. In three subsoils with comparatively low pH and intermediate to high redox potential, atrazine was transformed gradually, to leave 1·9%, 6·2% and 17·5% of the dose after about five years. In one of these subsoils, hydroxy-atrazine was detected; the amount corresponded to half of the dose of atrazine. In one anaerobic subsoil with high pH, the transformation of atrazine was comparatively fast (half-life about 0·15 year). Another anaerobic subsoil, with similar pH and a somewhat higher redox potential, however, showed hardly any transformation. Sterilization of the first anaerobic subsoil had no effect on the rate of transformation. In the course of about five years, bentazone in the first three subsoils was transformed gradually to leave <0·25%, 11% and 25% of the dose. Bentazone transformation in the two subsoils with high pH and low redox potential was very slow, but the presence of oxygen in one of these subsoils speeded up the transformation. © 1998 SCI     

Mineralization of 2,4‐D,mecoprop, isoproturon and terbuthylazine in a chalk aquifer

The potential to mineralize 2,4‐dichlorophenoxyacetic acid (2,4‐D), mecoprop, isoproturon and terbuthylazine was studied in soil and aquifer chalk sampled at an agricultural field near Aalborg, Denmark. Laboratory microcosms were incubated for 258 days under aerobic conditions at 10 °C with soil and chalk from 0.15–4.45 m below the surface. The [ring‐U‐¹⁴C]‐labeled herbicides were added to obtain a concentration of 6 µg kg^?1 and mineralization was measured as evolved [¹⁴C]carbon dioxide. The herbicides were readily mineralized in soil from the plough layer, except for terbuthylazine, which was mineralized only to a limited extent. In the chalk, lag periods of at least 40 days were observed, and a maximum of 51%, 33% and 6% of the added 2,4‐D, mecoprop and isoproturon, respectively, were recovered as [¹⁴C]carbon dioxide. Large variations in both rate and extent of mineralization were observed within replicates in chalk. No mineralization of terbuthylazine in chalk was observed. As a measure of the general metabolic activity towards aromatic compounds, [ring‐U‐¹⁴C]‐benzoic acid was included. It was readily mineralized at all depths. © 2000 Society of Chemical Industry     

Evaluation of groundwater sustainability based on groundwater age simulation in the Zhangye Basin of Heihe River watershed,northwestern China

Water resources, as the primary limiting factor, constrain the economic and social development in arid inland areas. The Zhangye Basin is a representative area of inland river basins, which is located in the middle parts of the Heihe River watershed, northwestern China. Facing with the huge water shortage, people exploited ground- water at a large scale in recent years. The reducing recharge from surface water and over-exploitation of ground- water led to the decline of groundwater levels and threatened the sustainability of water resources. This study con- structed a conceptual and numerical groundwater flow model and calibrated the model based on the observed wells. A solute transport model was built using MT3DMS to calculate the groundwater age distribution in the Zhangye Basin. The simulated result shows that the youngest groundwater is distributed near the most upstream areas in the model domain, which is less than 1,000 a, older groundwater is distributed in deeper parts of the aquifer and near the discharge outlets, ranging from 6,000 a to over 20,000 a. Spatial variation of groundwater ages in the middle area indicates the recharge diversity between unconfined and confined aquifer. Groundwater age can serve as an indicator to evaluate groundwater’s renewal capacity and sustainability. The formation of groundwater resources in the lower stream area would spend 10,000 a or even more than 20,000 a, so exploitation of groundwater in these areas should be restrained.     

考虑土体颗粒运动的承压含水层单井抽水数学模型及其解析分析

对于承压含水层单井抽水引起的含水层变形问题,以单元体变形为基础,建立了考虑含水层中颗粒运动的承压含水层单井抽水数学模型;提出了颗粒运动函数的概念,对特定的定解条件给出了解析解;推求出单井抽水含水层颗粒位移量的计算公式,通过算例对该模型进行了分析。结果表明,井壁颗粒逸出易导致井周含水层颗粒的较大位移;当抽水井井壁无颗粒逸出时,颗粒位移量的最大值并不在井壁处,而且,随着抽水时间的延续,其最大值也逐渐增大,其位置也向远离井周的方向推移。该模型可用于对抽水引起的地面沉降进行系统的预测和定量计算。