Effect Of Shallow Groundwater Research Articles

Effects of Shallow Groundwater on Deep Groundwater Dynamics in a Slow-Moving Landslide Site

A slow-moving landslide is a mass movement that has major societal impact because of its large sediment volume. The principal cause of landslides is increased pore water pressure in deep aquifer close to the slip surface. Elucidation of the behavior of deep groundwater is critical in the stability analysis of the slow-moving landslides. Shallow groundwater, which flows through the landslide regolith, can undergo vertical infiltration and thus make a major contribution to the formation of deep groundwater, but this has not been sufficiently elucidated. The aim of the present study was to investigate the effects of shallow groundwater on the dynamics of deep groundwater in a landslide regolith. At a landslide site, with an area of 4200 m2, the shallow and deep groundwater levels were observed. A 1-m-depth temperature survey and groundwater quality analysis were also performed. Water budget analysis using the groundwater level showed that in the former half of a major rainfall event, groundwater that infiltrates vertically in the landslide regolith plays a central role in raising the deep groundwater level. In addition, the preferential flow from shallow to deep aquifers is suggested to be important in that infiltration. The results of this study emphasize the importance of including the preferential flow from the shallow aquifer when modeling dynamics of deep groundwater.

Yield, Nitrogen Uptake and Nitrogen Leaching of Sensor-Based Fertigation-Cultured Tomato in a Shallow Groundwater Region: Effect of Shallow Groundwater on Tomato Irrigation

Fertigation with surface drip has been introduced and broadly applied for vegetable cultivation in the Eastern China, which presents high precipitation and always has shallow groundwater. To estimate the influence of high groundwater level on the tomato nitrogen (N) and water use efficiency and develop new sensor-based fertigation technology, experiments were executed in plastic greenhouse in the experimental farm of Yangzhou University located in the suburban of Yangzhou city during 2016-2017 growing seasons using a block randomization with three replications. Three N dosages and 4 watering treatments were carried out in this experiment. The data indicated that irrigation threshold of -35 kPa was optimum to get the maximum production of tomato. In this treatment, the value of estimated plant evapotranspiration (ETc) was much higher than total applied water volume, suggesting high groundwater table had a significant contribution on the tomato ETc and a sensor-based irrigation strategy should be more accurate than the simulated ETc irrigation method to calculate the water demand under this condition. In addition, our results indicated that high groundwater level had a positive effect to alleviating N leaching. Finally, we can conclude that fertigation technology enhanced the N use efficiency (NUE) and water use efficiency (WUE) and three fourths of the calculated N dosage (according to a traditional nutrient equation) was sufficient to optimize tomato yield.

Energy fluxes and evapotranspiration over irrigated maize field in an arid area with shallow groundwater

Precise estimations of energy fluxes and evapotranspiration for cropland in arid areas with shallow groundwater are necessary but limited. There is also a need to better understand the contribution of groundwater for meeting crop water consumptive use. In this study, considering the environmental conditions, such as meteorological variables, crop growth and water regimes, energy fluxes and actual evapotranspiration (ETa) in an irrigated maize field with shallow groundwater were examined using eddy covariance system during two growing seasons. Due to the energy imbalance of the eddy covariance method, latent heat (LE) was adjusted using the Bowen ratio preservation of energy principle and subsequently very close (R2 = 0.94) to that measured by the Bowen-ratio-energy-balance system. For seasonal and diurnal variations, LE accounted for the highest proportion of net radiation (Rn) from the jointing stage. While LE/Rn was a little lower in 2018 than that in 2017 which may be because of the deeper groundwater table depth (WTD) in 2018. The negative sensible heat in the afternoon implied the occurrence of heat advection in the irrigated cropland. Energy fluxes and ETa were significantly affected by crop development when leaf area index was less than about 4 m2 m-2. Moreover, the increasing WTD from 1.2 to 2.2 m decreased LE by about 70 % and increased daily average Bowen ratio. From the jointing stage, total ETa was 522.1 and 453.8 mm in 2017 and 2018, respectively. The inter-seasonal variation in ETa was more dependent on water conditions than the potential evaporative demand. The water balance result showed that average WTD of 1.52 and 1.76 m for the growing period contributed to 36.3 % and 26.2 % ETa in 2017 and 2018, respectively. Besides, daily groundwater contribution between two seasons was different because of the differences in irrigation allocation and WTD. These results highlight the key effect of shallow groundwater to energy fluxes and water exchange of agroecosystem in arid areas.

Enhancing the capability of hydrological models to simulate the regional agro-hydrological processes in watersheds with shallow groundwater: Based on the SWAT framework

This article introduces the SWAT-AG (a modified SWAT for agro-hydrological modeling) as an enhanced hydrological model for simulating the hydrological processes in agricultural watershed with shallow water tables. The model is developed based on the framework of the SWAT with significant improvements on describing the interactions of the vadose zone water, groundwater, salt and plant growth. The main features of the SWAT-AG include that it can simulate the close interactions of soil water and shallow groundwater with considering the capillary rise effects; it provides functions to simulate the soil salt movement and salt-stress on plant growth; and it incorporates a balance-based module on a sub-basin scale for shallow aquifer with involving canal seepage and ditch drainage calculation. Model testing and application were conducted in Jiyuan Irrigation System located in the Hetao of upper Yellow River basin, northwest China. The comparison between simulated and observed data showed that the SWAT-AG performed well and obviously better than the original SWAT in simulating the soil water and salt dynamics, groundwater depth fluctuations, and plant growth and water consumption. The results showed that the NSE averagely increased from −17.57 to 0.57 and from 0.71 to 0.79 for soil water storage and leaf area index, respectively, in typical croplands and natural patches. In addition, the effects of shallow groundwater in sustaining the agro-ecosystems were reasonably revealed with the spatial analysis of evapotranspiration, capillary rise and salt accumulation. The test case proved that the proposed SWAT-AG could efficiently enhance the functionality and practicality of hydrological models for agricultural watersheds with shallow groundwater.

Yield, nitrogen uptake and nitrogen leaching of tunnel greenhouse grown cucumber in a shallow groundwater region

The middle and lower reaches of Yangtze River present high rainfall and always have a high water table. Recently drip fertigation has been introduced and widely used for vegetable production in this area. To investigate the effect of shallow groundwater and the newly-developed fertigation on the cucumber water and nitrogen (N) requirement, experiments were carried out in plastic tunnels in Yangzhou, Jiangsu, China, during the 2016 and 2017 growing seasons using a randomized block design with three replicates. Four N rates, 4 irrigation amounts and 2 irrigation intervals (2 d and 4 d) were applied in this experiment. The results showed that irrigation amount of 75% of estimated plant evapotranspiration (ETc) was optimal to obtain the highest yield, indicating shallow groundwater had a considerable contribution to the cucumber plant evapotranspiration in this condition. Fertigation technology improved the irrigation water use efficiency (IWUE) and N use efficiency (NUE) and 75% of the recommended N rate (calculated according to a traditional local nutrient balance method) optimized cucumber yield. Frequent irrigation with low water volume had a beneficial impact on the improvement of cucumber yield, IWUE, NUE and reduced the N leaching. According to this work, the recommended fertigation strategy is 0.75 of recommended N, 0.75 estimated ETc and 2 d irrigation interval in this experiment, in which cucumber yield of 105.4 Mg ha−1, IWUE of 41.1 kg m-3 and NUE of 356.4 kg kg−1 were achieved.

Analyzing the Role of Shallow Groundwater Systems in the Water Use of Different Land-Use Types in Arid Irrigated Regions

Clarifying the role of shallow groundwater systems in eco-hydrological processes is of great significance to agricultural production and ecological sustainability. In this paper, a lumped water balance model was proposed for the GSPAC (groundwater-soil-plant-atmosphere-continuum) system for different land use types under arid, shallow water table conditions. Model application was conducted in an irrigation district (Jiyuan) located in the upper Yellow River basin. A 13-year (2001–2013) water balance calculation was carried out to quantify the water budgets of different land use types. The effects of shallow groundwater on water and salt exchanges among different land use patterns were analyzed. Results indicated the shallow groundwater systems played a significant role in water storage and supply, water and salt redistribution, and the salt accumulation and drainage in Jiyuan. About 36% of the total applied water was first stored in a shallow groundwater system, and then redistributed. After redistribution, 63% of the total diverted water was consumed by cropland evapotranspiration (ET), 20% by natural land ET; the rest was discharged through drainage or groundwater exploitation. Finally, 67% of the introduced salt accumulated in natural land, while the rest was drained away, which helped maintain the productivity of the croplands. Overall, our results have quantitatively revealed the multifaceted roles of shallow groundwater systems, and also suggested the key management concepts for sustaining agroecosystems in arid irrigated areas.

Untangling the effects of shallow groundwater and deficit irrigation on irrigation water productivity in arid region: New conceptual model

Water scarcity and salt stress are two main limitations for agricultural production. Groundwater evapotranspiration (ETg) with upward salt movement plays an important role in crop water use and water productivity in arid regions, and it can compensate the impact of deficit irrigation on crop production. Thus, comprehensive impacts of shallow groundwater and deficit irrigation on crop water use results in an improvement of irrigation water productivity (IWP). However, it is difficult to quantify the effects of groundwater and deficit irrigation on IWP. In this study, we built an IWP evaluation model coupled with a water and salt balance model and a crop yield estimation model. As a valuable tool of IWP simulation, the calibrated model was used to investigate the coupling response of sunflower IWP to irrigation water depths (IWDs), groundwater table depth (GTDs) and groundwater salinities (GSs). A total of 210 scenarios were run in which five irrigation water depths (IWDs) and seven groundwater table depths (GTDs) and six groundwater salinities (GSs) were used. Results indicate that increasing GS clearly increases the negative effect on a crop's actual evapotranspiration (ETa) as salt accumulation in root zone. When GS is low (0.5–1g/L), increasing GTD produces more positive effect than negative effect. In regard to relatively high GS (2–5g/L), the negative effect of shallow-saline groundwater reaches a maximum at 2m GTD. Additionally, the salt concentration in the root zone maximizes its value at 2.0m GTD. In most cases, increasing GTD and GS reduces the benefits of irrigation water and IWP. The IWP increases with decreasing irrigation water. Overall, in arid regions, capillary rise of shallow groundwater can compensate for the lack of irrigation water and improve IWP. By improving irrigation schedules and taking advantages of shallow saline groundwater, we can obtain higher IWP.

Estimating the effect of shallow groundwater on diurnal heat transport in a vadose zone

The influence of shallow groundwater on the diurnal heat transport of the soil profile was analyzed using a soil sensor automatic monitoring system that continuously measures temperature and water content of soil profiles to simulate heat transport based on the Philip and de Vries (PDV) model. Three experiments were conducted to measure soil properties at depths of 5 cm, 10 cm, 20 cm, and 30 cm when groundwater tables reached 10 cm, 30 cm, and 60 cm (Experiments I, II, and III). Results show that both the soil temperature near shallow groundwater and the soil water content were effectively simulated by the PDV model. The root mean square errors of the temperature at depths of 5 cm, 10 cm, and 20 cm were 1.018°C, 0.909°C, and 0.255°C, respectively. The total heat flux generated the convergent and divergent planes in space-time fields with valley values of–161.5W•m–2 at 7:30 and–234.6W•m–2 at 11:10 in Experiments II and III, respectively. The diurnal heat transport of the saturated soil occurred in five stages, while that of saturated-unsaturated and unsaturated soil profiles occurred in four stages because high moisture content led to high thermal conductivity, which hastened the heat transport.

Untangling the effects of shallow groundwater and soil texture as drivers of subfield‐scale yield variability

AbstractWater table depth (WTD), soil texture, and growing season weather conditions all play critical roles in determining agricultural yield; however, the interactions among these three variables have never been explored in a systematic way. Using a combination of field observations and biophysical modeling, we answer two questions: (1) under what conditions can a shallow water table provide a groundwater yield subsidy and/or penalty to corn production?; and (2) how do soil texture and growing season weather conditions influence the relationship between WTD and corn yield?. Subfield‐scale yield patterns during a dry (2012) and wet (2013) growing season are used to identify sensitivity to weather. Areas of the field that are negatively impacted by wet growing seasons have the shallowest observed WTD (<1 m), while areas with consistently strong yield have intermediate WTD (1–3 m). Parts of the field that perform consistently poorly are characterized by deep WTD (>3 m) and coarse soil textures. Modeling results find that beneficial impacts of shallow groundwater are more common than negative impacts under the conditions studied, and that the optimum WTD is shallower in coarser soils. While groundwater yield subsidies have a higher frequency and magnitude in coarse‐grained soils, the optimum WTD responds to growing season weather at a relatively constant rate across soil types. We conclude that soil texture defines a baseline upon which WTD and weather interact to determine overall yield. Our work has implications for water resource management, climate/land use change impacts on agricultural production, and precision agriculture.

Review of Floods in a Changing Climate: Extreme Precipitation by Ramesh S. V. TeegavarapuCambridge University Press, New York; 2013; ISBN 978-1-107-01878-5; 285 pp., $120.00.

Review of <i>Floods in a Changing Climate: Extreme Precipitation</i> by Ramesh S. V. TeegavarapuCambridge University Press, New York; 2013; ISBN 978-1-107-01878-5; 285 pp., $120.00.

Reconnoitering the effect of shallow groundwater on land surface temperature and surface energy balance using MODIS and SEBS

Abstract. The possibility of observing shallow groundwater depth and areal extent using satellite measurements can support groundwater models and vast irrigation systems management. Moreover, these measurements can help to include the effect of shallow groundwater on surface energy balance within land surface models and climate studies, which broadens the methods that yield more reliable and informative results. To examine the capacity of MODIS in detecting the effect of shallow groundwater on land surface temperature and the surface energy balance in an area within Al-Balikh River basin in northern Syria, we studied the interrelationship between in-situ measured water table depths and land surface temperatures measured by MODIS. We, also, used the Surface Energy Balance System (SEBS) to calculate surface energy fluxes, evaporative fraction and daily evaporation, and inspected their relationships with water table depths. We found out that the daytime temperature increased while the nighttime temperature decreased when the depth of the water table increased. And, when the water table depth increased, net radiation, latent and ground heat fluxes, evaporative fraction and daily evaporation decreased, while sensible heat flux increased. This concords with the findings of a companion paper (Alkhaier et al., 2012). The observed clear relationships were the result of meeting both conditions that were concluded in the companion paper, i.e. high potential evaporation and big contrast in day-night temperature. Moreover, the prevailing conditions in this study area helped SEBS to yield accurate estimates. Under bare soil conditions and under the prevailing weather conditions, we conclude that MODIS is suitable for detecting the effect of shallow groundwater because it has proper imaging times and adequate sensor accuracy; nevertheless, its coarse spatial resolution is disadvantageous.

Improving irrigation water operation in the lower reaches of the Amu Darya River – current status and suggestions

AbstractIrrigated agriculture is widespread in the Central Asian drylands and important for food security of the region. However irrigation practices based on rules made for cotton production on large units do not provide adequate guidance for the now widespread small farms that produce cotton wheat and rice. Excessive unsustainable water use is the consequence. Land and water resource management practices were analysed in 2006 for the irrigated area (approx. 1885 ha) of a water users' association (WUA) as a case study. The Shomakhulum WUA is situated in the Khorezm region Uzbekistan in the Aral Sea Basin. The designed water allowance of 0.40 l s−1 ha−1 was 46% higher than the 0.21 l s−1 ha−1 required in 2006. A ponding experiment conducted at two locations under typically shallow groundwater conditions showed that actual seepage losses in the major distributing canal (Pakhtakiyar) in the WUA were about 2% at one site and negative at the other. This does not support the present blanket recommendation of an additional 29% of water to compensate for anticipated seepage losses. Considering the effects of shallow groundwater the seasonal leaching requirements were estimated at 200 mm versus the 400 mm based on the blanket local recommendations for a 14 ha cotton field. However the actually applied water amounted to 670 mm which exceeds the calculated requirements by 235% and the local recommendation by 68%. The findings showed (i) excessive irrigation water supply and in turn high wastage owing to an underestimation of the potential shallow groundwater contribution (ii) overestimation of conveyance losses and (iii) excessive leaching due to outdated knowledge on leaching requirements when compared to standards. We suggest that the outdated water allowance the inaccurate estimation of the conveyance efficiency and excessive water applications during leaching cause a waste of precious fresh water and a rise in the shallow groundwater levels which consequently increases secondary soil salinity. The revision of irrigation and leaching norms combined with an improved knowledge on seepage dynamics under shallow groundwater levels is needed before any further recommendations can be made to the farmers in order to reach the objective of sustainable agriculture in the area. Copyright © 2011 John Wiley &amp; Sons Ltd.

A qualitative description of shallow groundwater effect on surface temperature of bare soil

Abstract. Whether or not shallow groundwater affects skin temperature (the temperature of soil surface) is important to detect depth and extent of shallow groundwater by dint of remote sensing and important for land surface modelling studies. Although few studies have been conducted to investigate that effect, they have yielded contradicting conclusions and they stopped in 1982. To determine that shallow groundwater affects skin temperature, we measured soil temperature at two different depths (5 and 10 cm) in seven places with variable water table depths every ten minutes and for six days. After that, we correlated the minimum, maximum and average daily temperatures to average groundwater depth. We also built a simple numerical model using a differential equations solver, Flex PDE, to simulate heat transfer into soil profile and used it to simulate groundwater effect on skin temperature. We found quite high negative correlation between the maximum and average daily soil temperature and groundwater depth. Contrarily, we could hardly find any correlation between the daily minimum temperature and groundwater depth. Numerical simulations, though simple, were useful in showing that groundwater shifted skin temperature curves up in the winter and down in the summer without affecting the shape of the curve. We conclude that shallow groundwater affects skin temperature directly by its distinctive thermal properties in the soil profile and indirectly by affecting soil moisture which in turn has many different and contradictory effects on skin temperature. This study recommends building a comprehensive numerical model that simulates the effect of shallow groundwater on skin temperature and on the different energy fluxes at land surface.

Response of upland rice to soil and hydrological conditions on a footslope in central ivory coast

In the typical toposequence (upland, footslope and bottomland) of West Africa's vast interior plains and plateaus, research on rice-based cropping systems has largely been confined to upland and bottomland. This article deals with potential and actual rice production on a coarse sandy footslope with temporarily shallow groundwater in central Ivory Coast. Measured soil physical and hydrological properties were used to simulate the response of upland rice to water supply at different positions of the footslope. Simulation gave a potential production (water and nutrients not limiting) of 5500 kg/ ha and a water-limited yield (nutrients not limiting) of 4950–5500 kg/ha. The beneficial effects of shallow groundwater during the cropping period in overcoming mid-season dry spells are confined to the central and lower parts of the footslope. Measured rice yields were 750 kg/ha (unfertilized) and 1620 kg/ha (NPK fertilizer). Next to a low inherent availability of nitrogen at the research site (0.3 g/kg ), N use efficiency of the rice crop was low (52 kg grain/kg N), and also N fertilizer recovery was low (18%), in spite of its application in three splits. It is argued that leaching and denitrification contributed considerably to losses of N from the cropped land, partly as a result of prolonged humid conditions during the growing period.