Application of visual,statistical and artificial neural network methods in the differentiation of water from the exploited aquifers in Kuwait

The ability of artificial neural network to differentiate water samples from the two aquifers of Kuwait on the basis of their major ion chemistry has been demonstrated. The major ion concentration distribution in the groundwater of the Kuwait Group and the Dammam Formation aquifers of Kuwait appears very similar. Cross-plots, supported by the discriminant function analysis of the data, however, suggest that there are some subtle differences in the overall composition of the water from the two aquifers that make it possible to differentiate the water from the two aquifers in almost 80% of the cases. An artificial neural network improved the differentiation capability to 90% of the cases. It is also possible to estimate the fraction of Kuwait Group water in the flow stream of dually completed wells with the help of an artificial neural network developed for this purpose. Electronic Publication     

Land subsidence caused by groundwater exploitation in Suzhou City,China

Suzhou City, located at the lower reaches of the Yangtze River in southeastern Jiangsu Province, is one of the few cities in China which suffer from severe ground settlement. A research project was carried out to investigate this problem. Geological and hydrogeological studies show that there is a multi-layered aquifer system with three distinct, soft mud layers of marine and lagoonal origins. An examination of historical records of groundwater extraction, water levels, and ground settlement shows that the ground subsidence is associated with the continuously increasing groundwater extraction in the deep, confined aquifer. It is believed that the consolidation of the soft mud layers, especially the third layer which is thick and close to the main pumped aquifer, contributes to the ground settlement. A three-dimensional finite difference numerical model representing the multi-layered aquifer system was developed to study the ground settlement in response to groundwater extraction. By calibrating the model with both the measured groundwater level and ground settlement, the aquifer parameters were estimated. The model outputs fit reasonably well with the observed results, which indicates that the numerical model can reproduce the dynamic processes of both groundwater flow and soil consolidation. The hydraulic conductivity of the third mud layer near the center of the ground settlement has been reduced by over 30% in the last 14 years. The gradual deterioration in the hydraulic conductivity of the mud may have significant adverse effect on the sustainable groundwater resource of the deep confined aquifer, since the recharge from the shallow aquifers through the mud layer is the only source of water to the deep aquifer. An analysis of the spatial distributions of groundwater drawdown and ground settlement shows that the area with maximum drawdown is not necessarily the area with maximum ground settlement due to the occurrence of the soft mud layer. A simple reallocation in pumping rates on the basis of the spatial distribution of the thick mud layer could significantly reduce the ground settlement. Electronic Publication     

Hydrochemical and isotopic characteristics of groundwater in the Souss Upstream Basin, southwestern Morocco

Heterogeneous shallow Plio-Quaternary formations of the Souss Plain represent the most important aquifer in southern High Atlas Mountains in Morocco. The present work was conducted in the Souss Upstream Basin to identify the chemical characteristics and the origin of groundwater in an aquifer under semi-arid climate. Isotopic and hydrochemical compositions combined with geological and hydrogeological data were used for this purpose. The total dissolved solids vary from 239 to 997 mg l⁻¹, and the following groundwater types are recognized: Ca²⁺–Mg²⁺–HCO₃⁻, Ca²⁺–Mg²⁺–SO₄²⁻ and Ca²⁺–Mg²⁺–Cl⁻. The groundwater is saturated and slightly supersaturated with respect to carbonate minerals and undersaturated with respect to evaporite minerals, which means that the groundwater composition is largely controlled by the dissolution of carbonate rocks known in the basin. The isotopic contents of groundwaters ranged from −8‰ to −5.2‰ for δ¹⁸O, from −52‰ to −34‰ for δD, and from 0 to 5.5 TU for tritium. The hydrogen (δD) and oxygen (δ¹⁸O) isotope signatures reveal a significant infiltration before evaporation takes place, indicating a major recharge directly from fractures in the crystalline and limestone formations of Atlas Mountains (above 800 m a.s.l.) and infiltration of surface water in the alluvial cones at the border of the Atlas basins. The very low tritium values suggest that the groundwater recharge follows a long flow path and a mixing between old and modern water is shown. However, a slight evaporation effect is noted in the southern part of the basin close to the Anti-Atlas Mountains.     

Paleohydrology of arid southeastern maui, hawaiian islands, and its implications for prehistoric human settlement

Arid slopes on the southeastern side of Maui are densely covered with archaeological remains of Hawaiian settlement from the late prehistoric to early postcontact period (ca. A.D. 1500-1860). Permanent habitation sites, agricultural features, and religious structures indicate perennial occupation and farming in a subregion called Kahikinui, yet there is presently no year-round water source. We explore the possibility that postcontact deforestation led to the loss of either (1) perennial channel flow or (2) perennial springs or seeps. To investigate the first possibility, we estimated ancient peak flows on 11 ephemeral channels in Kahikinui using field measurements and paleohydrology. Peak-flow estimates (3-230 m³/s) for a given drainage area are smaller than those for current perennial Maui streams, but are equivalent to gauged peak flows from ephemeral and intermittent streams in the driest regions of Hawai’i and Maui islands. This is consistent with the long-term absence of perennial channel flow in Kahikinui. On the other hand, others have shown that canopy fog-drip in Hawai’i can be greater than rainfall and thus a large part of groundwater recharge. Using isolated live remnants and snags, we estimate the former extent of the forest upstream from archaeological sites. We use rough estimates of the loss of fog-drip recharge caused by deforestation and apply a simple, steady-state hydrologic model to calculate potential groundwater table fall. These order-of-magnitude estimates indicate that groundwater could have fallen by a minimum of several meters, abandoning perennial seeps. This is consistent with archaeological evidence for former perennial seeps, such as stonewalls enclosing potential seeps to protect them. Although longer-term reductions in rainfall cannot be ruled out as a factor, deforestation and loss of fog-drip recharge are obvious and more immediate reasons for a recent loss of perennial water in Kahikinui, Maui.     

丽江7.0级地震地下流体异常特征

通过对１９９６年２月３日云南丽江Ｍｓ７．０地震前震中周围水位、水氡、水汞、泉点宏观等地下流体共７１个台项观测资料的异常及综合特征分析，初步认为震前异常数量较多，异常时间分布具有整体性、同步性、集中性的特点，但异常主要集中在短期阶段，临震异常不突出；突间分布具有集中性和非均匀性，孕震区至远场影响区的异常比例最高，震源区内为相对“盲区”，且突出而肯定的宏观异常极少；异常的时空演变特征复杂，总体没有规律     

链子崖T_8－T_（12）缝段地下水的侵蚀性及其工程对策

在简述地形地貌、气象水文、构造部位和岩石组成等地质环境因素的基础上．本文重点研究了链子崖危岩体煤层采空区地下水的水化学类型及其对工程结构的侵蚀等级．并提出了地上排水、地下排水与采用抗侵蚀工程材料等综合的工程治理对策。     

Porewater pressure increases in soil and rock from underground chemical and nuclear explosions

A review and analysis of chemical and nuclear explosive-induced porewater pressure increases and induced rise in groundwater table elevations (groundwater mounding) is presented. Our analysis indicates that residual pore pressure increases and groundwater mounding can be induced by underground chemical and nuclear explosions to scaled distances of 879 m/(kt)^1/3. This relationship is linear over seven orders of magnitude of explosive energy ranging from a 0.01 kg chemical explosion to a 100 kt nuclear explosion and is valid for a wide variety of saturated geological profiles. Underground chemical explosions, and probably underground nuclear explosions have the potential to induce liquefaction of water-saturated soils to scaled distances of about 260 m/(kt)^1/3.     

Paleocollapse structure as a passageway for groundwater flow and contaminant transport

 Paleocollapse structure is a rock collapse, resulting from the failure in the geological history of the bedrock overlying karstified limestone. Depending on the present hydrogeological conditions within the area of paleocollapse and the internal properties of these structures, they can provide a means to facilitate groundwater flow and contaminant transport. Inactive paleocollapse structures can be reactivated by human activities such as dam construction, mining underground minerals, pumping groundwater, and development of landfills. They can also be reactivated by natural events such as earthquakes and neotectonic movements. In the mines of northern China, sudden inflow of karst water from Ordovician limestone into drifts and mining stopes through paleocollapse structures has caused significant economic loss. Water pumping tests and accompanied dye traces are effective approaches of locating water-conducting paleocollapse structures. Grouting is probably the best means of preventing them from becoming geohazards. Received: 26 November 1996 · Accepted: 17 June 1997     

Nitrogen isotope indicators of seasonal source variability to groundwater

 A nitrogen isotope study of soil water and groundwater in southern Indiana, USA, in 1991–1992 demonstrated considerable variations in nitrate degradation processes compared to an earlier investigation in 1986–1987. Although N-fertilizers were applied in May 1991, the δ¹⁵N values in soil water decreased in February 1992, indicating its delayed release into the system after substantial rainfall. The δ¹⁵N values of groundwater decreased from +12.3‰ in November 1991 to +11.3‰ in February 1992, and to +7.5‰ in March 1992. The increased residence time of nitrate in the soil resulted in increased denitrification, ammonia volatilization and plant uptake, and reduced threat to the groundwater quality. The 1986–1987 study in the area reported that excessive rainfall during the summer rapidly transported the nitrate to deeper horizons and drastically reduced volatilization and microbial reduction of nitrate, thus increasing the immediate threat to the groundwater quality in the area. The present study demonstrated that nitrogen isotopic signatures can be used to determine the effects of local soil type, rainfall, and land-use practices on the fate of nitrate in the subsurface. Received: 18 February 1997 · Accepted: 17 June 1997     

Groundwater acidification in Triassic sandstones: prediction with MAGIC modelling

 Acidification of groundwater lags behind acid deposition due to the relatively long water residence time in conjunction with various buffering processes in the soil zone and deeper aquifer (chemical weathering, cation exchange, sulfate sorption, and N uptake by the biomass). Extensive field data from eight forested catchments in the Bunter Sandstone of the Black Forest, including results from water budget studies and hydrochemical analysis of stream and spring waters, were used to simulate the future evolution of ground-water acidification with the MAGIC model. The present acid deposition exceeds the “critical load” (here meaning buffering due to chemical weathering and protonation of organic acids) in six of eight catchments. Two catchments are well buffered because they contain carbonate-bearing layers in the Upper Bunter sandstone. Transient buffering (i.e., cation exchange, N uptake, the sulfate sorption) thus far prevents worse acidification, but this effect will decline in the future. For one of the poorly buffered catchments (Seebach), a two-layer simulation was carried out, based on extensive data from 10 years of measurements. Validation of the long-term simulations by hydrochemical and soil data was hampered by strong annual variations but generally supported by paleolimnological studies. In the future, reductions in the S deposition by 20% and the N deposition by 10% up to the year 2030 are assumed as the most probable scenario. N uptake through soil and vegetation will come to an end as suggested by decreasing C/N ratios of the organic matter. This process is arbitrarily included in the simulations. In the periglacial soil layer, acidification will decrease until the year 2030 and then approach a steady-state condition. In the fractured aquifer, acidification will also proceed at a decreasing rate; however, sulfate desorption up to the year 2130, the end of simulated period, will prevent earlier remediation. Despite a significant reduction in S deposition since the mid-1980s, further efforts are necessary to reduce the emission of acidifying substances. Liming in the recharge area is partially effective to ameliorate “shallow” groundwater but largely fails to ameliorate “deeper” groundwater in the sandstone aquifer. Received: 30 July 1996/Accepted: 23 January 1997