Low Groundwater Table Research Articles

A Study of Maintaining and Improving the WASH Services Provided by Local and International Agencies in Selected Refugee Camps in Kurdistan Region, IRAQ

Hosting a massive number of refugee in Kurdistan Region of Iraq which is above 2 million people in both category of internal displaced people and refugees, while the technical and economical capacities of the local government are limited which results the provision of water, sanitation and hygiene challenging for both local people and the surrounding environment. The aim of this research is benchmarking the current WASH services in the existing refugee camps, identifying the major difficulties within WASH service provision and highlighting the impact of current WASH practices on physical environment. The intervention of this research includes the camps in both Erbil and Sulaimanyah provinces of Iraqi-Kurdistan. The international and local agencies have been evaluated regarding WASH services provision in selected refugee camps. Detailed interviews were conducted with 6 service provision agencies’ representatives to record their approaches while, questionnaire was administered among 395 refugees in addition with personal observation to determine at what extend the services are adequate and sustainable. It has been observed that both local and international organizations claimed to have sufficient WASH services but on ground, there are big challenges facing the process of WASH service provision. In general, it has been found that, most of the service providers are not concern with environmental risks which may cause by lack of sufficient WASH services. . There are several environmental issues in the camps, including lowering groundwater table, and increasing soil pollution as a result of unmanaged wastewater disposal and Excreta management. Public health problems in the camps are due to dispose black water into the pits while the groundwater is the main water supply source in the refugee camp. Keywords: Water, Sanitation, Hygiene, Environment, Waste Management, Groundwater

Drivers of carbon sequestration by biomass compartment of riparian forests

Riparian forests are expected to play a crucial role in the global carbon (C) cycle but the complex mechanisms of C sequestration in forests remain poorly understood. This study used a comprehensive approach to analyze C sequestration that included the main C compartments in forests, i.e., litterfall, fine roots, and aboveground woody biomass. We aimed at modeling each of them in response to an array of environmental drivers to untangle the functioning of C sequestration by compartment. The study was conducted in a Central European riparian forest that is part of the Donau‐Auen National Park in Austria. Carbon sequestration by compartment was correlated with environmental parameters (climate, stream flow, hydrological, spatial, and forest stand parameters) using generalized linear mixed models (GLMM), and the correlations were prioritized by hierarchical partitioning. Our results suggest divergent responses of C sequestration in different ecosystem compartments under dry and wet soil conditions. In particular, dry conditions led to significantly higher C sequestration in aboveground woody biomass (larger distance to the low groundwater table), whereas wetter conditions fostered C sequestration in fine‐root (smaller magnitude of fluctuation in the groundwater table) and leaf biomass (smaller distance to the low groundwater table). Fine roots and litterfall responded to short‐term variations in climate (mean annual temperature) and flooding parameters (duration of the low to mean Danube River water level in the previous dormant season), highlighting the pivotal role of the dynamic fine‐root and leaf biomass compartments for C uptake in forest ecosystems. Consequently, litterfall and fine roots should be considered to improve the sensitivity of C sequestration model responses to climate scenarios.

Two and three-dimensional slope stability analyses of final wall for Miduk mine

In this research, Two and three-dimensional slope stability analyses of final slope for Miduk copper mine is investigated by using distinct element code. These analyses were repeated in three positions (dry- drained- wet) and were done for four walls of the mine; including eastern wall, northern wall, western wall and southern wall. The stability of Miduk copper mine walls were accomplished by distinct element code (UDEC&3DEC). Both 2D and 3D slope stability analyses were performed to establish the representative shear strength parameters to use in the analyses and to examine the differences in the results. The extended Mohr–Coulomb failure criterion was used for analyses. The rock mass was assumed to be permeable and also by the obtained data from surveying, laboratory tests and field observations. The results are as follows: - Water and pore pressure in the faults and main joints were the most important destabilizer factors in these analyses. - The factor of safety after the drainage improved (27–34) % and (20–28) % based on the 3D and 2D slope stability analyses, respectively. - The difference in factors of safety between the 2D and 3D slope stability analyses for the deeper groundwater table (water level in the elevation 2540 on the walls) is less than 7 %. The factors of safety obtained from 2D slope stability analyses are not necessarily more conservative than 3D slope stability analyses. Analyses of the slope after lowering of groundwater table by horizontal drains showed that the factor of safety of the slope has improved tremendously. The differences in factors of safety for 2D and 3D slope stability analyses are greater for low groundwater table as compared with those for high groundwater table. The results illustrated how 3D slope stability analyses have become less daunting to perform and can be incorporated into routine slope designs.

Odvisnost velikosti prevodnih elementov doba (Quercus robur L.) od temperatur na dveh rastiščih Querco-Carpinetum v Sloveniji

The aim of our study is to fully investigate the relationship between mean monthly temperatures and vessel features. Two vital and one declining groups of pedunculate oak from two Querco-Carpinetum sites in Slovenia are analyzed. Chronologies of mean vessel area and sum of vessel area were developed after previous high quality surface preparation and image analysis with macro EWVA in the ImageJ program. Declining group from Cigonca had the biggest average vessel and the largest amount of conductive tissue, which was linked to the dieback of this group. The analysis of temporal stability of correlation coefficients for declining group explained negative correlations, which were not stable in time. All groups were most responsive to the April temperatures. For all groups, climate signal was the strongest in the mean vessel area parameter. For vital group from Mlače we can expect, in the event of continuous rising of mean temperatures, bigger mean vessels that are more likely to be affected by cavitation. Lower ground water table in 1982 at Cigonca coincides with the reduced climate signal in the vessels.

Nondestructive Measurement of Water Content and Moisture Migration of Unsaturated Red Clays in South China

To reveal the moisture migration mechanism of the unsaturated red clays, which are sensitive to water content change and widely distributed in South China, and then rationally use them as a filling material for highway embankments, a method to measure the water content of red clay cylinders using X-ray computed tomography (CT) was proposed and verified. Then, studies on the moisture migrations in the red clays under the rainfall and ground water level were performed at different degrees of compaction. The results show that the relationship between dry density, water content, and CT value determined from X-ray CT tests can be used to nondestructively measure the water content of red clay cylinders at different migration time, which avoids the error reduced by the sample-to-sample variation. The rainfall, ground water level, and degree of compaction are factors that can significantly affect the moisture migration distance and migration rate. Some techniques, such as lowering groundwater table and increasing degree of compaction of the red clays, can be used to prevent or delay the moisture migration in highway embankments filled with red clays.

Forests in a water limited world under climate change

The debate on ecological and climatic benefits of planted forests at the sensitive dry edge of the closed forest belt (i.e. at the ‘xeric limits’) is still unresolved. Forests sequester atmospheric carbon dioxide, accumulate biomass, control water erosion and dust storms, reduce river sedimentation, and mitigate small floods. However, planting trees in areas previously dominated by grassland or cropland can dramatically alter the energy and water balances at multiple scales. The forest/grassland transition zone is especially vulnerable to projected drastic temperature and precipitation shifts and growing extremes due to its high ecohydrological sensitivity. We investigated some of the relevant aspects of the ecological and climatic role of forests and potential impacts of climate change at the dryland margins of the temperate-continental zone using case studies from China, the United States and SE Europe (Hungary). We found that, contrary to popular expectations, the effects of forest cover on regional climate might be limited and the influence of forestation on water resources might be negative. Planted forests generally reduce stream flow and lower groundwater table level because of higher water use than previous land cover types. Increased evaporation potential due to global warming and/or extreme drought events is likely to reduce areas that are appropriate for tree growth and forest establishment. Ecologically conscious forest management and forestation planning should be adjusted to the local, projected hydrologic and climatic conditions, and should also consider non-forest alternative land uses.

Summer droughts limit tree growth across 10 temperate species on a productive forest site

Studies on climate impacts on tree annual growth are mainly restricted to marginal sites. To date, the climate effects on annual growth of trees in favorable environments remain therefore unclear despite the importance of these sites in terms of forest productivity. Because species respond differently to climate, comparing a multitude of species further enhances our knowledge on climate impacts on tree growth and forest productivity.We present a first study that reveals to what extent radial growth is limited by climate and the groundwater table across 10 temperate tree species growing on a uniform, productive soil (i.e. high nutrient and water contents) in the Netherlands. We ranked our study species according to their shade tolerance, which is associated with species’ resource requirements and growth rates, and examined their annual growth using tree-ring analysis. This allowed us to investigate how these species with diverse ecological backgrounds differ in their growth response to precipitation, temperature, irradiance, potential evapotranspiration (PET), and the groundwater table, when growing under similar and favorable site conditions.Nine out of 10 species had strikingly similar radial growth rates (on average 3.9–4.8mmyr−1), which contradicts the widely established trade-off between shade tolerance and growth. Populus trichocarpa, the least shade-tolerant of our species, however grew much faster (on average 6.8mmyr−1). Trees of all species reduced their growth significantly during dry summers, driven by low rainfall and high PET. Yet, the magnitude of their growth responses to climate conditions and especially the groundwater table differed across species. Receding groundwater tables significantly and strongly reduced radial growth of the shade-intolerant species, but not of the shade-tolerant species. The climate impacts on growth were not associated with variation in shade tolerance across our species.Our study demonstrates that even on a productive forest site, summer droughts reduced radial growth across a multitude of common tree species, whereas lower groundwater tables only affected the shade-intolerant species significantly. Thus, the productivity of forests in favorable environments may be seriously affected when summers in north western Europe become hotter and drier as predicted by climate models.

Fine root and aboveground carbon stocks in riparian forests: the roles of diking and environmental gradients

We analysed current carbon (C) stocks in fine root and aboveground biomass of riparian forests and influential environmental parameters on either side of a dike in the Donau-Auen National Park, Austria. On both sides of the dike, carbon (C) stock of fine roots (CFR) under four dominant tree species and of aboveground biomass (CAB) were assessed by topsoil cores (0–30 cm) and angle count sampling method respectively (n = 48). C stocks were modeled, performing boosted regression trees (BRT). Overall CFR was 2.8 t ha−1, with significantly higher C stocks in diked (DRF) compared to flooded riparian forests (FRF). In contrast to CFR, mean CAB was 123 t ha−1 and lower in DRF compared to FRF. However, dike construction was consistently ruled out as a predictor variable in BRT. CFR was influenced by the distance to the Danube River and the dominant tree species. CAB was mainly influenced by the magnitude of fluctuations in the groundwater table and the distances to the river and the low groundwater table. Despite pronounced differences in FRF and DRF, we conclude that there is only weak support that dikes directly influence C allocation in floodplain forests within the time scale considered (110 years).

Catchments in the future North: interdisciplinary science for sustainable management in the 21st Century

Catchments in the future North: interdisciplinary science for sustainable management in the 21^st Century

Simulation and Evaluation of Ecohydrological Effect of Water Transfers at Alagan in Lower Tarim River

The riparian vegetation is highly dependent on the groundwater which is recharged by the river in arid regions. Water is the most important limiting factor for riparian vegetation in arid regions. From 1970s to 2000, the lower Tarim River almost dried up and the groundwater table fell down obviously. The riparian vegetation degraded seriously due to the low groundwater table. From 2000 to 2006, water transfers were implemented in the lower Tarim River to restore the ecological environment. Although the observation of groundwater and vegetation was carried out along lower Tarim River, the dynamics of the groundwater and vegetation along the cross section of the river were unknown. Ecohydrological evolution model on Riparian Vegetation in hyper-arid regions (ERV model) is a distributed ecohydrological model and has been validated at Yingsu in lower Tarim River. In this paper, the ERV model is applied to analyze the ecohydrological effect of water transfers at Alagan in lower Tarim River. At the same time, the ERV model is further validated. The simulation result is validated by observed groundwater table and vegetation coverage computed from remote sensing data. The result shows that the average groundwater table at Alagan increased by 4.74m from 2000 to 2006 and the average groundwater depth reached 6.36m. The average vegetation coverage increased from 0.130 to 0.194. In order to recover the green corridor, the further water transfers are required. The results are helpful for the ecohydrological research and water resources management in lower Tarim River.

Large-scale laboratory investigation into the effect of varying back-barrier lagoon water levels on gravel beach morphology and swash zone sediment transport

It is generally accepted that the effect on beach morphology of the interactions between swash motion and the beach groundwater table depends on the elevation of the latter relative to that of the sea. Specifically, a low beach groundwater table is considered to enhance onshore sediment transport and beach accretion, while the reverse is thought to hold for a high beach groundwater table. Here, we use the results of a carefully designed series of tests conducted in the Delta Flume, the Netherlands, as part of the Barrier Dynamics Experiment (BARDEX), to unequivocally demonstrate the validity of this assertion. During the experiment, a 4-m high and 50-m long gravel barrier (D50=11mm) was constructed within the central region of the 250-m long and 7-m deep wave flume, enabling a back-barrier ‘lagoon’ to be located at its landward side. The groundwater table in the beach was manipulated by lowering and raising the lagoon level, and the gravel beach was subjected to variable wave conditions and sea/lagoon levels. Using as the initial beach profile the morphology resulting from 90min of wave forcing with the sea and lagoon at the same level, the identical wave forcing with a low lagoon level consistently resulted in onshore sediment transport in the swash zone and beach accretion, whereas the identical wave forcing with a high lagoon level consistently caused offshore sediment transport in the swash zone and beach erosion. The divergent beach morphological responses for the low and high lagoon levels could not be attributed to changes in the ‘bulk’ swash hydrodynamics (i.e., based on single-point velocity measurements) arising from a difference in the amount of swash infiltration into the unsaturated beach. Instead, application of a sediment transport model that accounts for the effects of in/exfiltration suggested that the onshore sediment transport and beach accretion for the low lagoon tests mainly resulted from enhanced bed shear stresses during the wave uprush due to infiltration into the saturated part of the beachface. Due to the large hydraulic conductivity of gravel (K=O(0.1ms−1)), the effect of altered shear stresses due to in/exfiltration may be an important factor in sediment transport in the swash zone of gravel beaches.

Two and three-dimensional slope stability reanalyses of Bukit Batok slope

A residual soil slope in Singapore that failed on two occasions, in 1989 and 1991, was reanalysed using two (2D) and three-dimensional (3D) slope stability analyses. The geometry of the slope in 1989 differed from that in 1991. The 2D and 3D slope stability analyses on the slope that failed in 1989 showed that the average shear strength parameters of the residual soils are representative of the slope and the factors of safety obtained from 2D slope stability analyses are not necessarily more conservative than 3D slope stability analyses. The analyses also showed that the slope failed in 1989 due to rising groundwater table. The analyses of the slope in 1991 showed that the slope experienced shallow failure due to the high groundwater table. Analyses of the slope after lowering of groundwater table by horizontal drains showed that the factor of safety of the slope has improved tremendously. The differences in factors of safety for 2D and 3D slope stability analyses are greater for low groundwater table as compared with those for high groundwater table. The results illustrated how 3D slope stability analyses have become less daunting to perform and can be incorporated into routine slope designs.

MODELLING OF LAND SUBSIDENCE ALONG TANAH MAS -PELABUHAN SECTION SEMARANG CITY USING FINITE ELEMENT METHOD

Land subsidence has been an apparent problem in the northern part of Semarang city, Central Java, which has caused enormous physical and economical impacts. This area is underlain by alluvium sediments of clay, silt, sand and gravel. The nature of the alluvium soil is soft and highly compressible which induces natural consolidation to occur. The lowering of groundwater table due to exploitation and loads of building and earth fill accelerate the rate of consolidation settlement. A study of land subsidence modeling was carried out in the northern part of Semarang city. Collection and analysis of data on the geology, hydrology, soil properties and monitored settlements were conducted. Modeling of land subsidence involved stress deformation analysis using finite element method. The settlements computed for selected section of the city of Semarang were compared with measurements of settlement in the city area. The simulation results appear to be in reasonably good agreement with the measurement results. Simulation results at selected section indicated that the contribution of lowering groundwater table factor accounts for less than 50% of total monitored subsidence. Meanwhile simulation results using application of external loading and lowering of groundwater table showed better agreement with the monitored subsidence. Information of magnitude and factors causing land subsidence is important particularly for city planning purposes.

Effects of climate change on evapotranspiration and soil water availability in Norway spruce forests in southern Finland: an ecosystem model based approach

ABSTRACTNorway spruce (Picea abies) is sensitive to decreases in soil water availability. In this study, we simulated how the climate change may influence the hydrological processes with impacts on the growth of Norway spruce in three sites located in southern Finland (61oN). The sites differed from each other in regard to the climate and soil water conditions; however, the initial structure of the tree stands was similar. Under the current climate, the canopy surface evaporation (Ec) increased, whereas the transpiration (Et) remained at a constant rate over the simulation period, as the seedlings in the initial stand grew to full maturity. Under the changing climate, on average, the cumulative of Ec and Eg (evaporation from soil surface) were 16% and 14% higher than those under the current climate, respectively, whereas the cumulative Et was 12% lower. The leaf area index (L) increased constantly on the sites with high (SH) and medium (SM) soil moisture, unlike on the site with low (SL) soil moisture. The canopy conductance (gcs) declined rapidly and earlier on the site SL, which implied the acclimation of stomatal behaviour to drought. The increasing water loss through evaporation decreased the water infiltration into the soil profile, resulting in an increasing soil water deficit (Wd), especially on the site SL. It also occurred earlier in all three sites under the changing climate. It was predicted that climate change will create a suboptimal environment for Norway spruce in southern Finland, particularly on the upland sites with lower groundwater table. Copyright © 2011 John Wiley & Sons, Ltd.

Causes and Effects of Gully Erosion on Agricultural Lands and the Environment

This study was aimed at assessing the causes of the gully erosion and its effects on the agricultural lands in the arid region of southeastern Iran. In this study, we have used geologic maps in scales of 1:50,000 and 1:250,000, aerial photographs on a scale of 1:20,000, field observation, and GPS (global positioning system). Three soil samples were taken from 25, 50, and 75% of the gully length at each location and analyzed for pH, electrical conductivity (EC), exchangeable sodium percentage (ESP), sodium absorption ratio (SAR), cation exchange capacity (CEC), calcium (Ca), and soil texture. The causes of gully erosion, its effects on agricultural lands, characteristics of the gullies, soil depth, and vegetation of each area were evaluated. The results show that several parameters, including poor rangeland vegetation cover, overgrazing, human activities, intensive and short-period rainfall, improper land use, improper irrigation design, improper discharge of water in the channels, and soil characteristics influence the gully erosion. Gully erosion causes severe damage to agricultural lands, including soil loss, increase in surface runoff, lower soil water-holding capacity, lower quality and quantity of water, lower groundwater table, and lower agricultural production. It increased migration from villages to cities and increased socioeconomic problems and poverty. It also caused substantial damages to construction sites such as bridges, roads, and settlements as well as rivers and reservoirs and increased sediment concentration in rivers.

Simulating the Effect of Sulfate Addition on Methylmercury Output from a Wetland

The watershed analysis risk management framework (WARMF) model was applied to Wetland S6 of the Marcell Experimental Forest, using the data from a field experiment, conducted to investigate the effect of sulfate additions on mercury methylation in the wetland. The wetland was modeled as interconnected land catchments. Actual meteorology data and mercury and sulfate concentrations of precipitation were input to the model. To simulate the sulfate sprinkling, the experimental section of the bog was irrigated with sulfate water on the actual dates of sulfate additions. The model simulated wetland outflows that matched the measured outflows with an R -square of 0.856. WARMF also simulated other phenomena observed in the experiment: higher sulfate and MeHg levels at the wetland outlet after every sulfate addition, and higher sulfate and MeHg levels in the pore water of the bog after only the May addition, not the July and September additions. According to WARMF, the low groundwater table in May allowed the spri...

Linking water sources with foliar nutrient status in upland plant communities in the Everglades National Park, USA

AbstractPlant communities within an ecosystem can vary in water source usage and nutrient availabilities, thus permitting community coexistence and diversity. We investigated the differences in water source utilization in two ecologically important upland plant communities: tropical hardwood hammocks and pine rocklands in the predominantly flooded Everglades ecosystem. We then linked these differences with their foliar nutrient levels and photosynthetic performance as measured by δ13C abundance. Based on a comparison of δ18O of plant stem waters with those of potential water sources (nutrient‐poor groundwater and nutrient‐rich water in organic litter referred to as soilwater), we observed that during the wet season hammock plants relied on soilwater while in the dry season they relied on groundwater. A similar seasonal shift was observed in pineland plants, however, groundwater constituted the major part of water uptake throughout the year except for late wet season. Consistent with the nutrient concentration of different water sources used in the two communities, hammocks had a greater annual mean foliar nitrogen and phosphorus concentration at the community level over pinelands as well as a higher leaf area index. High foliar N concentration in hammock plants was associated with eventual stomatal limitation of photosynthesis. Hammock species being intolerant of flooded soils are restricted to water uptake in the shallow unsaturated soil layer in the wet season, yet access the lowered groundwater table in the dry season. This dependence on a relatively narrow annual range of water table levels should be considered in South Florida water management and Everglades restoration. Copyright © 2009 John Wiley & Sons, Ltd.

Validation of a large scale hydrological model with data fields retrieved from reflective and thermal optical remote sensing data – A case study for the Upper Rhine Valley

For the entire Upper Rhine Valley between Karlsruhe and Basel, a long term simulation (1985–2002) with the GWN_BW model (partly physically based 1-D water balance model) resulted in the retrieval of the following hydrological process variables: daily potential and actual evaporation, surface runoff from sealed surfaces and groundwater recharge. Meteorological data has been interpolated from all available stations in France, Germany and Switzerland including the mountainous regions of the Vosges Mountains and the Black Forest. The primary grid size of the model was 500 m; for landuse, the sub-grid variability has been taken into account additionally. In an alternative approach, Landsat-5 TM scenes from two different acquisition dates were integrated to model the daily rates of actual evaporation ( E a). To this end, data fields retrieved from both the thermal and reflective Landsat channels were combined with ancillary meteorological and digital elevation data. Assuming a single layer canopy-soil system, the daily E a rates were estimated from the modelled net radiation and the differences between maximum surface and maximum air temperatures; the final partitioning of sensible and latent heat fluxes was strongly determined by the pixel-wise derived vegetation abundances. The results of the remote sensing approach were compared quantitatively to the E a rates provided by the hydrological model by means of both correlation and geostatistical pattern analysis. Extreme differences between both approaches were detected. The low spatial variability of the simulated E a was explained by the parameterisation scheme for surface resistances. In total, the hydrological model often underestimated E a due to a non realistic representation of soil water availability under deciduous forests and a missing representation of irrigation. In addition, a static and very simple representation of capillary rise of groundwater was found to cause large overestimates of the modelled E a during periods with low groundwater table.

Nitrate in upper groundwater on farms under tillage as affected by fertilizer use, soil type and groundwater table

Indicators are needed to check whether policies on protection of groundwater are effective and if regulations are complied with. We evaluated various indicators at different scales, both in space and in time, and at different degrees of complexity. Groundwater was sampled on 34 arable farms for 3 years. Nitrate concentration in upper groundwater was low on clay soil. On sandy soil, peat layers reduced the nitrate concentration with about 80 mg/l on average. Sandy soils with high groundwater tables had nitrate concentrations that were less than half of those at sandy soils with low groundwater tables. The relationship between different fertilization variables and nitrate in groundwater was investigated for sandy soils without peat layers. N surplus poorly correlated with nitrate concentrations in groundwater when individual sampling points were studied, but clearly increased when data were averaged at the farm level. Soil mineral nitrogen correlated best with nitrate concentrations in groundwater. The relationships show that especially on well drained soil drastic measures will be inevitable to reach good water quality.

Late Quaternary history of the coastal Wahiba Sands, Sultanate of Oman

AbstractContinental sediments and geomorphological features of the coastal Wahiba Sands, Sultanate of Oman, reflect environmental variability in southeastern Arabia during the late Quaternary. Weakly cemented dune sands, interdune deposits and coastal sediments were dated by luminescence methods to establish an absolute chronology of changes in sedimentary dynamics. The dating results confirm previous assumptions that during times of low global sea level sand was transported by southerly winds from the exposed shelf onto the Arabian Peninsula. Two prominent phases of sand accumulation in the coastal area took place just before and after the last glacial maximum (LGM). A final significant period of dune consolidation is recognised during the early Holocene. However, no major consolidation of dunes appears to have occurred during the LGM and the Younger Dryas. In the northern part of the Wahiba Sands, these two periods are characterised by substantial sand deposition. This discrepancy is explained by the lack of conservation potential for dunes in the coastal area, probably caused by a low groundwater table due to low sea level and decreased precipitation. While the times of aeolian activity reflect arid to hyper‐arid conditions, lacustrine and pedogenically altered interdune deposits indicate wetter conditions than today caused by increased monsoonal circulation during the Holocene climatic optimum. Copyright © 2005 John Wiley & Sons, Ltd.