Water Table Depletion Research Articles

SOCIO-ECONOMIC EFFECTS OF WATER SCARICITY IN TEHSIL KARAZAT DISTRICT PISHIN BALOCHISTAN

In the globally changing scenario water is becoming scarier and important due to its nonavailability for the communities in almost every corner of the world. Focusing on the importance of the water a research was conducted on the socio-economic effects of water table depletion in Pishin Balochistan. primary data was collected through a questionnaire,secondary data from different generals, line departments and reports, the finding were discussed in focus group discussions in Karezaat and analyzed. Due to agrarian society absolute majority of people are engage with agriculture and they are irrigating their agriculture fields through tube wells by pumping the underground water through electric motor pumps that resulted in the water table depletion and change in agriculture productivity in the area. Which directly affect the socio economic conditions of the people of area like effect on children education, local traditions, and migration is taking place to urban centers. The unemployment, poverty and crime rate is increased. The Water Table in the area could be improved by the introduction, adoption and expansion of low delta crops, best water management practices, strictly implementation and monitoring of tube wells installation rule and regulation, diversify the means of livelihood.

The contribution of MRS and resistivity methods to the interpretation of actual evapo‐transpiration measurements: a case study in metamorphic context in north Bénin

ABSTRACTA quantitative budget estimate of actual evapo‐transpiration is a key issue for enhanced hydrological modelling in northern Bénin. Actual evapo‐transpiration is estimated using large aperture scintillometer equipment, devoted to sensible heat flux measurements. However, a previous study reported that the actual evapo‐transpiration cycle is not fully understood. Indeed, the actual evapo‐transpiration depends strongly on several factors such as climate, vegetation pattern, soil water storage and human activities. The respective contributions of the aquifer and vadose zone to the actual evapo‐transpiration budget are not known. When using piezometric variations of the water table, the aquifer contribution is not easy to quantify since the specific yield may vary in the investigated area, located in a metamorphic rock environment. In the present study, we investigate whether significant differences in the aquifer’s specific yield could exist within the large aperture scintillometer measurement area, leading to different actual evapo‐transpiration water losses. We use joint frequency electromagnetic resistivity mapping, geological surveys and magnetic resonance sounding (MRS) to delineate the effective porosity of the regolith around the scintillometre measurement area. Thirteen MRS soundings implemented in key areas reveal a clear classification of the main geological units on the basis of their water content. The MRS water content varies between 1.5–3% for amphibolite and micaschists formations to more than 12% for quartzitic fractured formations, whereas the MRS relaxation time is less discriminating (150–250 ms), indicating a small variation in pore size. Then, as a first modelling exercise, we assumed that the MRS water content (the effective porosity) maximizes the specific yield. The actual evapo‐transpiration budget given by a previous study (Guyot et al. ) is then re‐interpreted using geophysical data: we found that a) the measured water table depletion can explain the actual evapo‐transpiration value providing enough water for the transpiration process and b) the significant discrepancies in actual evapo‐transpiration signals observed between the eastern and western parts of the watershed can be explained by the respective effective porosity of the geological units. Even if further research is needed to link MRS water content to the specific yield and to evaluate a possible role of the deep vadose zone, the hydrogeophysical mapping presented in this study highlights the role of the MRS method for providing relevant information to understand hydrological processes in this complicated geological context of north Bénin.

Development of a tool for managing groundwater resources in semi‐arid hard rock regions: application to a rural watershed in South India

AbstractUntil recently, aquifers located in hard rock formations (granite, gneiss, schist) were considered as a highly heterogeneous media, and no adequate methodology for groundwater management was available. Recent research studies have shown that when hard rocks are exposed to regional and deep‐weathering processes and when the geology is relatively homogenous, a typical hard rock aquifer is made of two main superimposed hydrogeological layers each characterized by quite homogeneous specific hydrodynamic properties: namely the saprolite and the fissured layers. Therefore, for these cases, hard rock aquifers can be considered as a multi‐layered system. Based on these works, an operational decision support tool (DST‐GW) designed for the management of groundwater resources in hard rock area under variable agro‐climatic conditions has been developed. The tool focuses on the impact of changing cropping pattern, artificial recharge and rainfall conditions on groundwater levels at the scale of small watersheds (10 to about 100 km2 in case well‐developed weathering profile). DST‐GW is based on the groundwater balance and the ‘water table fluctuation method’, which are well‐adapted methods in hard rock and semi‐arid contexts. Based on field data from an overexploited South Indian watershed (58 km2), the model allows calibrating, at watershed scale, the variation in specific yield of the aquifer with depth, as well as the rainfall‐aquifer recharge relationship. Seasonal basin‐scale piezometric levels are computed with an average deviation of ± 0·56 m compared to measurements from 2001 to 2005. The model shows that, if no measure is taken, the water table depletion will induce the drying‐up of most of the exploited borewells by the year 2012. Scenarios of mitigation measures elaborated with the tool show that change in cropping patterns could rapidly reverse the tendency and lead to a sustainable management of the resource. This work presents the developed tool and particularly the hydraulic model involved in and its application to a case study. However, the purpose tool is applicable at watershed scale but not design for the groundwater management of a very small area or for a single borewell. Copyright © 2010 John Wiley & Sons, Ltd.

The effect of 1991-2001 droughts on ground water in Neishabour plain

Abstract This research investigates the effect of drought on ground water table of Neishabour plain. The precipitation data of Nishabour synoptic station during 1990-2001, the Bar climatology station during 1964-2001 and the data of hydrometric stations of Kherv and Bar in 1996-2001 have been used as the base of analysis. The method of Herbest et all has been used to analyze the drought. Using the effective precipitation and effective flow, the date of start and end of drought for the study region has been specified and then the time and intensity of drought have been calculated. The analysis shows that the main reason for the fall of the underground waters table level is the irregular use for agricultural consumptions. The climatic drought has had a direct effect on running water and it has also had direct effect on underground water of the region with a time lag. It was appeared that alluvial fan areas of Neishabour plain have a less decrease compared with the central and southern areas in spite of much consumption of water by deep wells. Key words: Climatic drought; Effective precipitation; Depletion of water table; Hydrograph; Ground water

Drought stress and recovery of riparian cottonwoods due to water table alteration along Willow Creek, Alberta

A 5-m-deep gravel pit was excavated from 1996 to 1998 in the floodplain between Willow Creek, Alberta, and a grove of balsam poplars ('cottonwoods', Populus balsamifera L.) and water level at the pit was lowered 2.5 m through pumping. This interrupted the infiltration of stream water into the riparian groundwater and imposed drought stress on the cottonwoods. Trees in the drought-affected grove displayed extensive leaf senescence and abscission in late August 1998, while trees in nearby control groves remained green until autumnal senescence in late September. The precocious senescence was accompanied by a two-thirds reduction in leaf stomatal conductance (g s) but mid-day leaf xylem water potentials (ψl) were only slightly reduced (−1.55 vs 1.42 MPa). Pumping ceased in 1999, the pit was partially refilled, and the hydraulic linkage between the stream and the riparian zone recovered. Subsequently in August 1999, g s and ψl were similar for trees in the affected and control groves and senescence phenologies were similar in 1999 and 2000. Annual branch growth increments varied 3-fold across years between 1994 and 1999, but there was no reduction in these growth increments in the drought-affected trees in 1998 or 1999. This study supports the hydraulic linkage between a stream and the adjacent riparian zone in a semi-arid region and demonstrates the vulnerability of riparian cottonwoods to drought due to water table depletion. It also indicates rapid physiological recovery of cottonwoods following restoration of water availability.

Groundwater Situation in India: Problems and Perspective

Overexploitation of groundwater and intensive irrigation in major canal commands has posed serious problems for groundwater managers in India. Depletion of water tables, saltwater encroachment, drying of aquifers, groundwater pollution, water logging and salinity, etc. are major consequences of overexploitation and intensive irrigation. It has been reported that in many parts of the country the water table is declining at the rate of 1-2 m/year. At the same time in some canal commands, the water table rise is as high as 1 m/year. Deterioration in groundwater quality by various causes is another serious issue. Increased arsenic content in shallow aquifers of West Bengal reported recently has created panic among the groundwater users. Summed together, all these issues are expected to reduce the fresh water availability for irrigation, domestic and industrial uses. If this trend continues unchecked, India is going to face a major water crisis in the near future. Realizing this, the Government of India has initiated several protective and legislative measures to overcome the groundwater management-related problems but, due to the lack of awareness and political and administrative will, none of the measures has made any significant impact. This paper highlights the critical issues and examines the various schemes related to groundwater development and management.

Water policy and environmental sustainability: the case of post‐colonial Namibia

AbstractIn semi‐arid countries, particularly in Africa, governments have evolved water policies oriented toward ‘techno‐giantist,’ grand‐scale schemes that have generally accelerated the depletion of national water tables. In Namibia, such a techno‐giantist water management strategy was utilized to reinforce the privileges of white minority farmers prior to independence, and was subsequently expanded to provide modern water facilities to the black African majority in the post‐independence period. The government has pursued not only the construction of a massive new system of pipelines and boreholes, but also the development of giant dam‐building and river canal schemes that are likely to result in watershed depletion over the long term. This reflects state leaders' belief in the imagery of political potency projected by the government's ability to build macro‐scale water systems. However, a water supply approach focused on more micro‐level extraction techniques through which aquifer recharge is prioritized is more likely to assure both local‐level water access and water table sustainability. Copyright © 2001 John Wiley & Sons, Ltd.

Simulated effects of water table and irrigation scheduling as factors in cotton production

Irrigation is essential for economic production of some crops in semiarid climates. Benefits from irrigation may be partially offset by detrimental effects of rising water tables and salinization. Drainage systems are usually installed when the water table rises to the root zone, but installation of a drainage system and safe disposal of drainage water are expensive. The long-term consequences of a high saline water table on crop production, particularly as related to irrigation scheduling, has not been firmly established. A multiseasonal transient state model, known as the modified van Genuchten-Hanks model, was used to simulate cotton (Gossypium hirsutum L.) production using a three or four in-season irrigation schedule (3irr or 4irr) under both free drainage and water table conditions. Under drainage conditions, irrigation scheduling to avoid applying more water than the soil water-holding capacity during any irrigation event is important, whereas this factor is less important under water table conditions. “Excess” water during an irrigation causes a rise in the water table, but this water remains available for later crop use which lowers the water table. In the presence of a water table the simulations indicate, (1) higher yields are achieved by applying less irrigation during the crop season and more during the preirrigation for salt leaching purposes, (2) annual applied water must equal evapotranspiration to avoid long-term water table rise or depletion, and (3) high cotton yields can be achieved for several years even if the water table is saline and no drainage occurs if the irrigation water is low in salinity.

Conflicts between wetland conservation and groundwater exploitation: Two case histories in Spain

The problems in two Spanish national parks located on wetlands are analyzed. The hydrogeological and ecological characteristics of the two parks are somewhat different as are their respective degrees of deterioration. The Tablas de Daimiel National Park is located on the Central Plateau of Spain. It used to consist of a marshy area of about 20 km2 around the confluence of two relatively small rivers. The area was marshy mainly because it was the natural discharge zone for a Tertiary aquifer system about 100 m thick extending over an area of some 5,000 km2, composed of calcareous and detrital material of continental origin. The average annual recharge has been estimated at approximately 350 hm3/yr. Current groundwater withdrawal is around 450 hm3/yr, mainly used to irrigate a surface area of some 1,000 km2. This overdevelopment has led to a continuous depletion of the regional water table and eventually to the drying out of the marshy area. Spontaneous combustion or fires caused by man have occurred in about 10 km2 of the desiccated areas since the spring of 1986. The Donana National Park is located on the estuary of the River Guadalquivir. The aquifer system of the Lower Guadalquivir estuary consists essentially of a permeable formation of unconsolidated Plioquaternary materials with an area of some 3,000 km2. Under the marshy area (about 1,800 km2) the aquifer system is confined below low-permeability estuary deposits which can be over 100 m thick. Around most of the marshland the aquifer crops out and is recharged by rain. The Donana National Park is over 700 km2 in size, part of which is in the marshland and part in the recharge area where the aquifer is phreatic. In the 1970s Spain's largest irrigation project using groundwater, covering a surface area of 240 km2, was planned in an area bordering on the national park. The initial project has been scaled down considerably as a result of protests by conservation groups. However, it seems likely that the water table depletion as a result of pumpage for irrigation could cause a large part of the ecotone situated at the contact-line between the marshland and the phreatic aquifer to disappear. This ecotone exists because it is a natural groundwater dischange area.