Unwatering the Divide Cut of the Tennessee-Tombigbee Waterway: A major challenge to construction

The construction of the Divide Cut of the Tennessee-Tombigbee Waterway required excavation of more than 150 million cubic yards of unconsolidated sand and clay To make this excavation required lowering the artesian groundwater table as much as 100 feet Lowering of the artesian head was accomplished with deep wells, while the gravity groundwater was removed by trenching Environmental considerations required predicting and monitoring the drawdown of groundwater in the area of the canal More than 1,000 piezometers were used to monitor construction excavation and the spread of the drawdown cone The 280-foot bottom width canal was successfully completed ahead of schedule with the groundwater safely controlled through permanent relief wells     

Subsurface dams to harvest rainwater— a case study of the Swarnamukhi River basin, Southern India

Declining water level trends and yields of wells, deterioration of groundwater quality and drying up of shallow wells are common in many parts of India. This is mainly attributed to the recurrence of drought years, over exploitation of groundwater, increase in the number of groundwater structures and explosion of population. In this subcontinent, the saving of water has to be done on the days it rains. India receives much of its rainfall in just 100 h in a year mostly during the monsoon period. If this water is not captured or stored, the rest of the year experiences a precarious situation manifest in water scarcity. The main objective behind the construction of subsurface dams in the Swarnamukhi River basin was to harvest the base flow infiltrating into sandy alluvium as waste to the sea and thereby to increase groundwater potential for meeting future water demands. An analysis of hydrographs of piezometers of four subsurface dams, monitored during October 2001–December 2002, reveals that there is an average rise of 1.44 m in post-monsoon and 1.80 m in the pre-monsoon period after the subsurface dams were constructed. Further, during the pre-monsoon month of June, much before construction of subsurface dams in October 2001, the water level was found fluctuating in the range of 3.1–10 m, in contrast to the fluctuation ranging from 0.4 to 3.1 m during the period following the construction of dams. Hence, the planning of rainwater harvesting structures entails thorough scientific investigations for identifying the most suitable locations for subsurface dams.     

Hydrology,hydraulic, and sediment considerations of the Tennessee-Tombigbee Waterway

The planning, design, and construction of the Tennessee-Tombigbee Waterway was a massive undertaking Ten locks and dams were constructed that form lakes with a total water surface area of over 42,400 acres The overall length of the waterway is 234 miles and required the excavation and disposal of over 307 million cubic yards of material Because of the magnitude of the project and the many factors and complexities involved, this article can only serve as an overview of the topics presented During the course of the development of the project, many design memoranda and reports were generated which portray the details of design Some of the more pertinent of these design documents are listed in the references.     

Recharge of groundwater through multi-stage reservoirs in a desert basin

Artificial recharge of groundwater through geologic formations is of interest in Jordan as it is a proven water resource management technique that increases the efficiency of water use. This paper documents the research conducted into designing a series of small recharge dams on three connected valleys. With 50 potential sites previously screened, the focus was on the final selected location in the Jordanian desert, in which detailed topographical and hydrogeological surveys were used to determine the optimal locations for construction of surface water retention structures. The research produced designs for an integrated system of seven 2.5-m dikes and one 5-m dam with a total potential recharge volume of 500,000 m³. Once constructed, these multi-stage reservoirs will conserve part of the water being lost and will provide additional groundwater for future use. The research fills a gap in the lack of standard designs that can be expanded and replicated in other areas in Jordan and elsewhere.     

Impact of rehabilitation of Assiut barrage, Nile River, on groundwater rise in urban areas

To make optimum use of the most vital natural resource of Egypt, the River Nile water, a number of regulating structures (in the form of dams and barrages) for control and diversion of the river flow have been constructed in this river since the start of the 20th century. One of these barrages is the Assiut barrage which will require considerable repairs in the near future. The design of the rehabilitation of the barrage includes a headpond with water levels maintained at a level approximately 0.60 m higher than the highest water level in the headpond of the present barrage. This development will cause an increase of the seepage flow from the river towards the adjacent agricultural lands, Assiut Town and villages. The increased head pond level might cause a rise of the groundwater levels and impedance of drainage outflows. The drainage conditions may therefore be adversely affected in the so-called impacted areas which comprise floodplains on both sides of the Nile for about 70 km upstream of the future barrage. A rise in the groundwater table, particularly when high river levels impede drainage, may result in waterlogging and secondary salinization of the soil profile in agricultural areas and increase of groundwater into cellars beneath buildings in the urban areas. In addition, a rise in the groundwater table could have negative impact on existing sanitation facilities, in particular in the areas which are served with septic tanks. The impacts of increasing the headpond level were assessed using a three-dimensional groundwater model. The mechanisms of interactions between the Nile River and the underlying Quaternary aquifer system as they affect the recharge/discharge processes are comprehensively outlined. The model has been calibrated for steady state and transient conditions against historical data from observation wells. The mitigation measures for the groundwater rise in the urban areas have been tested using the calibrated mode.     

Numerical modeling the role of rubber dams on groundwater recharge and phreatic evaporation loss in riparian zones

Rubber dams have been widely built for their advantages in increase of flooding resources utilization in the north arid and semiarid plain regions of China. Rise in river water stage by the dams, particularly during the drought periods, increases lateral seepage of river water into groundwater, and thus groundwater table and phreatic evaporation loss in the riparian zones. In this study, a riparian area of the Baihe River in Nanyang of Henan Province, China was selected for investigation of influences of the river dams on the groundwater recharge and evaporation loss. A hydraulic model, HEC-RAS, was used for simulation of the river stage variations along the Baihe River, and a numerical groundwater model, MODFLOW, was applied for simulation of groundwater dynamics and estimation of river flow seepage into aquifer and evaporation loss. The results show that the dams increase river stages of 2–3 m during January 2000–December 2002. The increase in the captured groundwater recharge was 7.15–34.06 million m³/a and the increased phreatic evaporation loss occupies 10% of the increased recharge when four rubber dams were built.     

The Dawson Cut Forest Bed in the Fairbanks area, Alaska, is about two million years old☆

The Dawson Cut Forest Bed lies in the lower part of thick, late Cenozoic loess deposits in the Fairbanks area. It is associated with several distal tephra beds that provide age control and offer the opportunity of its recognition elsewhere in central Alaska. EC tephra (named herein) occurs in the uppermost part of the Dawson Cut Forest Bed and its petrographic and chemical properties point to a co-magmatic relationship with PA tephra, which has not been found in direct association with the forest bed. Both tephra beds are pink and have unusually high Cl in their glass shards, which readily separates them from all other tephra beds in the Fairbanks area. They were produced by discrete eruptions, closely spaced in time. PA tephra has a glass-fission-track age of 2.02 ± 0.14 myr, indicating that the Dawson Cut Forest Bed must be about 2 million years old. The Palisades tephra (named herein) has very similar properties to these two tephra beds, suggesting that the buried forest bed just above it at the Palisades site on the Yukon River, about 250 km west of Fairbanks, correlates with the Dawson Cut Forest Bed.     

Climate change and groundwater resources in Myanmar

Myanmar is located in Southeast Asia within the Mekong River Basin. The estimated annual surface and groundwater potentials are 1 081 km3 and 494 km3, respectively. Based on geological conditions, 11 different types of aquifers have been classified in Myanmar. The recent alluvial formation, Irrawaddy formation, Upper Pegu Group and Plateau limestone formation are the major water-bearing geologic formations of the country. In Myanmar, 89% of the groundwater is used for agriculture, approximately 8% is used for domestic consumption, and 3% is used for industrial purposes. Climate change projections for Myanmar from 2001 to 2100 predict general increases in temperature, clear-sky days, rainfall variability and flooding risks and a greater occurrence and intensity of extreme weather events across the country. Additional technology and investments are required to achieve groundwater resource security in response to climate changes. In addition, methods of ensuring the sustainability of groundwater resources must be implemented via collaborations with other countries and international sources.     

滦河流域中上游富锶地下水成因类型与形成机制

承德市滦河流域富锶矿泉水资源丰富,成因类型多样,具有典型研究意义。通过水化学图解与多元统计分析、离子比值分析、矿物平衡体系分析,分析富锶地下水形成的地球化学背景,分区阐述富锶地下水水化学特征,探讨富锶地下水的形成机制。结果表明,研究区水化学类型以HCO3-Ca·Mg、HCO3·SO4-Ca、HCO3-Ca、HCO3·SO4-Ca·Mg为主。富锶地下水的形成受地质构造格局和岩浆活动控制,地质建造锶元素丰度影响,水文地球化学条件制约。断裂构造和地层岩性控制着富锶地下水形成分布的总体特征,水文地质条件影响着地下水化学锶元素的地球化学响应机制。地下水锶富集来源为含水介质长石矿物、碳酸盐矿物的风化溶解和阳离子交换吸附作用,矿泉水出露机制分为构造断裂深循环淋溶型、裂隙浅循环淋溶型、补给富集埋藏型3种类型。坝上高原孔隙裂隙水系统富锶地下水形成作用主要受大气降水和溶滤作用控制,滦河中上游裂隙水系统地下水阳离子交换吸附作用强烈,滦河中游孔隙岩溶裂隙水系统地下水化学主要受溶滤作用控制,蒸发浓缩作用和人为活动影响。     

A preliminary assessment of hydrogeological features and selected anthropogenic impacts on an alluvial fan aquifer system in Greece

An investigation was carried out to delineate the hydrogeologic framework and to understand groundwater quality of the Kompsatos River fan aquifer system, northeastern Greece, as well as to assess environmental impact induced by human activities. As groundwater is the only major source of water in this area, it is important to know the effect of geological formations, and anthropogenic activities on groundwater chemistry and environment. A thorough hydrogeological study was performed during the period 2004–2007. The differential river gauging method was used for estimating the volume of water leaking from (or discharging into) the river. Groundwater samples were collected from 89 monitoring wells, during the summer period of 2007, and analyzed for major ions and trace elements. A potential reservoir of groundwater is formed within the Kompsatos River fan. The aquifer system/Kompsatos River interaction is the outstanding feature of this area. Ca–Mg–HCO₃–SO₄ is the dominant water type as a result of dissolving carbonate salts. B, Ba, Mn, Li, Sr, and Zn are the most abundant trace elements in groundwater. Both the major-ion chemistry and trace element enrichment of the groundwater are controlled by mineral dissolution and water–rock interaction. Nitrate contamination of groundwater is related to agricultural practices. An improperly constructed drainage system led locally to salinization of groundwater. Channelization has caused considerable disruption to the river ecosystem. The eventual construction of a dam on the river will adversely affect the environment and the aquifer system. The lack of managerial policy for water is putting environmental resources and water supply in jeopardy.     

Displacement of the Great Divide in north Queensland associated with Neogene lava flows

In north Queensland, Australia, the ‘Great Divide’ forms the border between catchments draining into the Gulf of Carpentaria, including the Mitchell River, and those draining into the Coral Sea, including the Barron River. Until recently, it was commonly proposed that what is now the upper Barron River previously drained into the Mitchell River. However, little evidence was presented, and the assertion has been disputed. Our examination of borehole data, combined with accurate surveying of bedrock in the present Barron River channel, provides definitive evidence that paleochannels of the Mitchell River previously drained what is now the upper Barron River subcatchment. Lava that flowed down these channels at ca 1.79 Ma is evident in some of the boreholes and is exposed in the Barron River channel. The lava flows blocked the river channel, diverting the headwaters of the paleo-Mitchell River east into the Barron River, resulting in the western migration of the Great Divide. The consequent reduction in stream energy available to the truncated headwaters of Mitchell River has led to channel infill and aggradation of more than 40 m since the diversion of the Barron River. Subsurface paleochannels may be directing groundwater across the present drainage divide from the upper Barron River catchment into the Mitchell River catchment.     

Locating suitable sites for the construction of subsurface dams using GIS

Subsurface dams constitute an affordable and effective method for the sustainable development and management of groundwater resources when constructed on suitable sites. Such dams have rarely been constructed in crystalline rock areas and to best of our knowledge, geographic information system (GIS) has never been used in any methodology for locating suitable sites for constructing these dams. This paper presents a new methodology to locate suitable sites for the construction of subsurface dams using GIS software supported by groundwater balance modelling in a study area Boda-Kalvsvik, Sweden. Groundwater resources were calculated based on digitized geological data and assumptions regarding stratigraphic layering taken from well archive data and geological maps. These estimates were then compared with future extractions for domestic water supply using a temporally dynamic water balance model. Suitability analyses for subsurface dams were based on calculated topographic wetness index (TWI) values and geological data, including stratigraphic information. Groundwater balance calculations indicated that many of the most populated areas were susceptible to frequent water supply shortages. Of the 34 sub-catchments within the study area: ten were over-extracted, nine did not have any water supply demand at all, one was self-sufficient and the remaining 14 were able to meet the water supply demand with surplus storage capacity. Six suitable sites for the construction of subsurface dams were suggested in the vicinity of the over-extracted sites based on suitability analysis and groundwater balance estimates. The new methodology shows encouraging results for regions with humid climate but having limited natural water storage capacities. The developed methodology can be used as a preliminary planning step for subsurface dam construction, establishing a base for more detailed field investigations.     

Determining the seasonality of groundwater recharge using water isotopes: a case study from the upper North Han River basin,Korea

The stable isotopes of oxygen and hydrogen were used to determine the seasonal contributions of precipitation to groundwater recharge at a forested catchment area in the upper North Han River basin, Korea. A comparison of the stable isotopic signatures of groundwater and precipitation indicates that the precipitations which occurred during both the dry and rainy seasons are the important source of groundwater recharge in this region. A stable isotopic signature shown in the stream waters at the upstream reaches is similar to that of groundwaters, indicating that stream waters are mostly fed by groundwater discharge. Reservoir waters in the downstream flood control dams have lower deuterium excess values or d-values compared with those of the upstream waters, indicating a secondary evaporative enrichment. These results can provide a basis for the effective management of groundwater and stream water resources in the North Han River basin.     

气候变暖对黄河源区生态环境的影响

黄河源区位于多年冻土区,严酷寒冷的气候条件和冻土共同构建成一种特殊的冻结水环境,使地下水类型和水文地质结构均发生变化,与非冻土区有显著的差别,形成特殊的水文地质区。近几十年来,由于全球性气候温变暖,出现大面积冻土退化,以及过度放牧、鼠害加剧等原因,造成草场退化,沙漠化趋势日渐明显,严重地冲击着黄河河源区的水源养涵功能,导致黄河在源头段多次出现断流。通过水平衡计算,探讨了气候变暖对黄河源区多年冻土退化的影响,并阐述了冻结层上水环境变化和人类活动对生态环境的影响。     

Application of hydrochemical signatures to delineating portable groundwater resources in Ordos Basin, China

The Ordos Basin of China encompasses Shaanxi, Gansu, and Shanxi provinces, Ningxia and Inner Mongolia autonomous regions. It lacks significant surface water resources. Among the water-bearing formations, the Luohe formation, with an area of 1.32×10⁵ km², is the most prospective aquifer. Groundwater quality data collected at 211 boreholes drilled into the Luhe formation indicate a complex distribution of groundwater chemistry. The hydrochemical properties were used to study the recharge, runoff, and discharge conditions of the groundwater in Ordos Basin and to evaluate sustainable groundwater resources. In the northern part of the basin, the hydrochemistry types and the total dissolved solids (TDS) show a clear lateral transition from SEE to NWW, indicating that the groundwater gets recharge in the northwest region and discharges in the southeast region. In the southern part of the basin, maximum TDS occurs at the center of the Malian River valley, from which the TDS decreases radially. Therefore, the groundwater in the southern basin gets recharge from the southeast and southwest regions, and the Malian River valley is the discharge zone. As a result of this research, the areas with portable groundwater were delineated. They include most of the southeast region of the Sishili Ridge, east of the Ziwu Mountain, and the southwest corner of the basin. The TDS of the groundwater in these regions is less than 1 g/l, and the hydrochemistry type is either HCO₃ or HCO₃·SO₄.     

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     

The environmental effects of dam construction in tropical Africa: Impacts and planning procedures

Dam construction can have significant effects on downstream floodplain environments in tropical Africa. The impacts of river control on floodplain forests in the Tana River Valley in Kenya, and on floodplain agriculture in the Sokoto River Valley in Nigeria are described. The extent to which downstream impacts were understood or predicted in these case studies are described, and the implications of this for environmental appraisal in project planning are assessed.     

Identification and evolution of hydrogeochemical processes in the groundwater environment in an area of the Palar and Cheyyar River Basins,Southern India

The Palar and Cheyyar River Basins in Tamil Nadu state of Southern India are characterised by different geological formations, and groundwater is the major source for domestic, agricultural and other water-related activities. Hydrogeochemical studies were carried out in this area with the objective of identifying the geochemical processes and their relation to groundwater quality. Groundwater samples were collected once a month from 43 groundwater wells in this area from January 1998 to July 1999. Sampling procedures and chemical analysis were carried out as per the standard methods. Chemical data are used for mathematical calculations and graphical plots to understand the chemical process and its relation to the groundwater quality. The chemical composition of groundwater in the central part of the study area mainly depends on the recharge from lakes and the river, which is explained by a mixing mechanism. In addition, weathering of silicate minerals controls the concentration of major ions such as sodium, calcium, magnesium and potassium in the groundwater of this area. Further, the activity ratios indicate that the groundwater is in equilibrium with kaolinite, smectite and montmorrillonite. The reverse ion exchange process controls the concentration of calcium, magnesium and sodium in hard rock formations, and dissolution of carbonate minerals and accessory minerals is the source of Ca and Mg, in addition to cation exchange in the sedimentary formations. In general, the chemical composition of the groundwater in this area is influenced by rock–water interaction, dissolution and deposition of carbonate and silicate minerals, ion exchange, and surface water interactions.     

Differential Hydrogeological Effects of Draining Tunnels Through the Northern Apennines,Italy

Water inflows are a major challenge in tunnelling and particularly difficult to predict in geological settings consisting of heterogeneous sedimentary rock formations with complex tectonic structure. For a high-speed railway line between Bologna and Florence (Italy), a series of seven railway tunnels was drilled through turbiditic formations, ranging from pelitic rocks with thin arenitic layers over sequences including thick-bedded sandstone to calcareous rocks showing chemical dissolution phenomena (karstification). The tunnels were built as draining tunnels and caused significant impacts, such as drying of springs and base-flow losses at mountain streams. A comprehensive hydrological monitoring programme and four multi-tracer test were done, focusing on four sections of the tunnel system. The tracer tests delivered unprecedented data on groundwater flow and transport in turbiditic aquifers and made it possible to better characterize the differential impacts of tunnel drainage along a geological gradient. The impact radius is 200 m in the thin-bedded sequences but reaches 2.3–4.0 km in calcareous and thick-bedded arenitic turbidites. Linear flow velocities, as determined from the peaks of the tracer breakthrough curves, range from 3.6 m/day in the thin-bedded turbidites to 39 m/day in the calcareous rocks (average values from the four test sites). At several places, discrete fault zones were identified as main hydraulic pathways between impacted streams and draining tunnels. This case shows that ignoring the hydrogeological conditions in construction projects can cause terrible damage, and the study presents an approach to better predict hydraulic impacts of draining tunnels in complex sedimentary rock settings.     

Identifying environmental impacts of underground construction

Dewatering of the groundwater resource and associated reduced flow of surface water features are potential negative impacts when constructing underground facilities. Little work has been done to develop methods for the early detection of environmental impacts on water resources where major underground construction is being undertaken. Recognizing this, prior to construction of two rock tunnels in the southwestern USA, a 3-year preconstruction program was implemented to monitor over 100 wells, springs, and streams in the project area that might be affected. This preconstruction monitoring phase has established data for a hydrologic reference which indicates a high degree of spatial and temporal variability. This variability must be accounted for when trying to identify construction-related impacts. The project area was subdivided into areas of similar characteristics based on geologic and hydrologic features. Measurements from features within each unit were then normalized and aggregated to derive a single representative flow parameter. This representative flow was then correlated to precipitation and major stream flow records to allow for a method of estimating unimpacted flow and groundwater levels during and after construction. Application of this method proved useful in determining and enabling a quick response to construction-related impacts.