Lowering Of Groundwater Table Research Articles

Pedogenic evolution of paddy soils in different soil landscapes

Paddy soils are Hydragric Anthrosols and are an important soil resource for food production. They are widely distributed in China and Asia. Soils that can be used for paddy cultivation vary considerably but basically are grouped into three kinds of landscape, i.e., well-drained sloping uplands, alluvial plains with groundwater fluctuation, and poorly drained polder areas with a near-surface water table. Typical soil chronosequences were studied to clarify the pedogenic changes after wetland rice cultivation, especially in relation to management practices. All of them are in important rice production regions of China. The study focussed on redox condition and iron oxides dynamics. On alluvial plains, the soil conditions range from continuously reducing controlled by high groundwater to alternating reduction and oxidation because of artificial submergence and groundwater fluctuations. Artificially induced leaching losses, previously prevented by a high groundwater table, are partly compensated during paddy cultivation by the rejuvenation process of alluvial deposition. Soils on an older delta, which no longer receives river-sediments, are more strongly developed and showed a decrease of DCB-extractable iron in surface horizon of young paddy soils and more profoundly throughout the profile in old paddy soils. In the polder area, the apparent lowering of groundwater table by deposition of sediment has changed the soil hydrology and increased redox potential. With the better soil aeration, crystalline iron oxides and their ratio to total iron increase with cultivation age. On well-drained terraces, the change of soil moisture regime is overwhelming. Previously well-aerated upland soils are periodically reduced, which accelerates leaching and loss of iron oxides from surface horizons, and probably clay decrease by lateral movement and ferrolysis processes superimposed on the difference of parent soils. An iron-enriched subsurface horizon has formed rapidly and it is a diagnostic feature of this type of paddy soil.

Environmental effects induced by human activities in arid Shiyang River basin, Gansu province, northwest China

Shiyang River basin is located in Hexi Corridor, central-west Gansu province, northwest China. It is an area of typical arid to semiarid features. During the last century, especially the last half century, mankind's production activities have caused a series of detrimental environmental effects, which are summarized: water environment change, land desertification and salinization, and vegetation degeneracy. Changes in the water environment include the surface water system, water quantities, continuous lowering of the groundwater table and degradation of groundwater quality. Vegetation cover in the lower reaches is seriously degenerated, resulting in land desertification, salinization and dust storms. Analysis indicates that the rate of the groundwater table lowering in Shiyang River basin generally exceeds 0.3 m/year, and the mean annual rate of groundwater decrease in Wuwei and Minqing sub-basins reaches 1.11–3.98%. Until 1998, the shortage of groundwater volume was 4.526×108 m3. If no effective measures are taken, this figure will be 6.728×108 m3 in 2010. Remedial actions include: (1) recovery and protection of the water conservancy function of the mountain forests to ensure the sustainable development of this recharge area; (2) establishment of an authoritative agency to reasonably allocate the total water resources in Shiyang River basin; and (3) enactment of legislation and economic control to build up a water-saving society in Shiyang River basin.

Observation of underground water level in the area of forest estate "Sremska Mitrovica " during 2000 and 2001

Observation of underground water level in the area of "Jasensko-Belilo", which belongs to the Forest Estate "Sremska Mitrovica", started in 1999. The measurements were performed by means of 2 piezometers set up approximately perpendicularly to the river Sava, forming profile number 1 (Fig.1). The results of these measurements (Fig. 2, 3) show a significant lowering of groundwater level in 2000. The reason is most likely the unfavorable rainfall amount and distribution during that year (Table 2). A much better situation was during 2001 when the minimal groundwater level was up to 2 meters and it was considered to be the result of a favorable amount of rainfall and its distribution during the year (Tables 2, 3). It was noticed that Carpinus betulus appears instead of flowering ash (Fraxinus ornus), which is a good sign that generally the level of underground water is lowering. Also, the phenomenon that pedunculate oak (Quercus robur) gradually loses its natural regeneration capability also confirms the trend of lowering underground water level. If this trend continues, oak will be in a very near future naturally substituted by less valuable species, probably Turkey oak (Quercus cerris). If groundwater wells along the river Sava reach the vicinity of this area, which is a plan for the Belgrade city water supply, the trend of groundwater table lowering will be even more expressed and it will certainly endanger the existence of all valuable forest species in this area.

Moisture extraction pattern, phasic water use and phasic growth in groundnut(Arachis hypogaea) under varying moisture regime and groundwater table condition

An experiment conducted during summer 1992 and 1993 with groundnut (Arachis hypogaea L.) on moisture extraction pattern, phasic water use and growth at Chiplima showed that moisture extraction increased with lowering of groundwater table. On an average, crop extracted 18.6 cm water from 60 cm profile under 50 i 10 cm water table depth which increased to 25.2 cm and 26.7 cm at 90 i i 10 and 110 10 cm water table depth respectively. Extraction was the maximum (9.12 cm) at surface layer of 0 15 cm which accounted for 39.9% of the total extraction. It reduced to 7.31 cm (31.6%), 4.53 cm (1 8.7%) and 2.54 cm (9.8%) with increase in profile depth by 15 cm up to 60 cm profile respectively. Groundnut used the maximum water of 3.1 1 cmtday, with maximum growth in terms of crop growth rate (1 0.18 g/m2/day) and net assimilation rate (3.31 g/m2/d) during 56 90 days of its growth. Water use showed significant positive correlation with pod yield at lowest water table depth, r value of 0.994 being the maximum.

Prediction of groundwater table lowering for lignite opencast mining in a karstic terrain in western Macedonia, Greece : M. J. Kavvadas & P. G. Marinos, Quarterly Journal of Engineering Geology, 27 Suppl, 1994, pp 41–55

Prediction of groundwater table lowering for lignite opencast mining in a karstic terrain in western Macedonia, Greece : M. J. Kavvadas & P. G. Marinos, Quarterly Journal of Engineering Geology, 27 Suppl, 1994, pp 41–55

Ecological Responses of an Oligotrophic Floodplain Forest to Harvesting.

Aerial and ground-based harvest systems were compared in terms of effects on gaseous and hydrologic transfers of N and P. The South Alabama study sites were narrow floodplains of low order, blackwater streams and were dominated by P-deficient histolsols and a mixed deciduous, evergreen forest. There was no statistically significant harvesting effect on either denitrification or surface and groundwater chemistry. Denitrification exhibited a strong seasonal trend and considerable within-site variation with annual rates ranging from 7 to 20 kg/ha per yr. Nitrate and phosphate concentrations in waters were quite low and did not vary significantly between the harvested zone and unharvested forests immediately upstream and downstream from the harvest. An unexpected result of the harvests was a statistically significant lowering of groundwater tables, an apparent evaporation response to elevated temperatures in the dark-colored organic soils.

Prediction of groundwater table lowering for lignite open-cast mining in a karstic terrain in western Macedonia, Greece

Abstract Planning for the development of new lignite mines in the Ptolemais basin in western Macedonia, Greece, required the investigation of the hydrogeological characteristics of the adjacent karstic aquifer, since open-cast exploitation involves extensive and sustained groundwater table lowering (up to 260 metres). Review and evaluation of existing hydrological- hydrogeological data, in conjunction with the results of recent measurements, shows that groundwater flow is to the southeast in a single highly transitive karstified marble aquifer. An analytical regional flow model based on the finite element method is developed and used to assess the feasibility of the required groundwater table lowering and its effects on the hydrological budget of lake Vegoritis, nine kilornetres from the mines and in hydraulic continuity with the karstic aquifer. Model predictions show that the required ground water table lowering is not economically feasible at present and that any sustained large-scale dewatering scheme will significantly increase lake losses within a period of one to two years. It is thus concluded that exploitation of the new lignite- bearing horizons should not reach the karstic marbles at the boundary of the basin, but a zone of the relatively impermeable alluvium should be left to act as a seal. This scheme should be combined with partial lowering of the groundwater table to relieve the hydrostatic pressures on the seal, thus increasing the margin of safety against piping and slope failure.

Groundwaters in Location of Chernobyl Atomic Station and Their Contamination with Radionuclides after the Accident

An evaluation of the influence of the Chernobyl Atomic Power Station (APS) accident upon ground waters of meliorative systems was carried out in a 30 km zone around the station. At the locations where elevation exceeds 5 m, the danger of contamination is minimum in the first 5 years, which is why emphasis was placed on flood plains of river valleys. In flood plains the ground water table (GWT) before the accident varied from 0.2 to 3.3 m with fluctuation from 0.5 to 3 m. Since the accident the systems haven't been in operation, the GWT fluctuation amplitude has decreased, the period of high water table has lengthened, and locations with secondary waterlogging have appeared. The ground waters chemical composition influencing the migration and sorption processes is typical for surplus soil water regions: mineralization is up to 1.0 g/l and pH from 6 to 7.5. Ground waters are not naturally protected here against radionuclide migration because of the small thickness of aeration zone, the sandy and loamy composition of soils, and their low adsorption. In 1989 contamination of ground waters with caesium-137 amounted from 2.26 × 102 to 2.413x 103 Bq/m3 and with strontium-90 it was from 37 Bq/m3 to 3.66 × 104 Bq/m3. Radionuclide migration towards ground waters depends not so much on surface contamination intensity as on soil physical and chemical characteristics in the aeration zone. It appeared that there were no direct dependencies between soil surface contamination intensity and that of ground waters contamination. It was noted that the amount of radionuclides depends upon the season. Analysis of radionuclides concentration in ground waters at different depths, considering soil surface contamination, allows us to define a relatively safe level of GWT with initial contamination; this information contributes to working out the measures on GWT lowering to optimum levels.

Externality and equity implications of private exploitation of ground-water resources

Private exploitation of ground-water resources has several externality and equity effects. Four of these which have become particularly important in India are: (a) inequities caused by unequal access, (b) diseconomies caused by clustering of modern Water Extraction Mechanisms (WEMs) and permanent decline in water table due to excessive pumpage, (c) ingress of saline water into coastal aquifers due to lowering of ground-water table and (d) the potential that private WEMs offer to mitigate diseconomies in the form of water-logging and build-up of soil salinity in command areas of canals. Existing instruments of policy and the manner of their implementation are unlikely to be effective in managing these diverse effects. Public control of ground-water resource may, in theory, provide an alternative; however, existing evidence about management capacities available in the third world irrigation systems raises serious doubts about its viability. A third alternative aiming at managing these effects by influencing private returns to irrigation has been explored and developed.