Effects of water tables and nitrogen application on soil bacterial community diversity, network structure, and function in an alpine wetland, China

Nitrogen deposition and water tables are important factors to control soil microbial community structure.However,the specific effects and mechanisms of nitrogen deposition and water tables coupling on bacterial diversity,abundance,and community structure in arid alpine wetlands remain unclear.The nitrogen deposition(0,10,and 20 kg N/(hm^(2)•a))experiments were conducted in the Bayinbulak alpine wetland with different water tables(perennial flooding,seasonal waterlogging,and perennial drying).The 16S rRNA(ribosomal ribonucleic acid)gene sequencing technology was employed to analyze the changes in bacterial community diversity,network structure,and function in the soil.Results indicated that bacterial diversity was the highest under seasonal waterlogging condition.However,nitrogen deposition only affected the bacterial Chao1 and beta diversity indices under seasonal waterlogging condition.The abundance of bacterial communities under different water tables showed significant differences at the phylum and genus levels.The dominant phylum,Proteobacteria,was sensitive to soil moisture and its abundance decreased with decreasing water tables.Although nitrogen deposition led to changes in bacterial abundance,such changes were small compared with the effects of water tables.Nitrogen deposition with 10 kg N/(hm^(2)•a)decreased bacterial edge number,average path length,and robustness.However,perennial flooding and drying conditions could simply resist environmental changes caused by 20 kg N/(hm^(2)•a)nitrogen deposition and their network structure remain unchanged.The sulfur cycle function was dominant under perennial flooding condition,and carbon and nitrogen cycle functions were dominant under seasonal waterlogging and perennial drying conditions.Nitrogen application increased the potential function of part of nitrogen cycle and decreased the potential function of sulfur cycle in bacterial community.In summary,composition of bacterial community in the arid alpine wetland was determined by water tables,and diversity of bacterial community was inhibited by a lower water table.Effect of nitrogen deposition on bacterial community structure and function depended on water tables.

Exploring Soil Layers and Water Tables with Ground-Penetrating Radar

Ground-penetrating radar (GPR) has been used predominantly for environments with low electrical conductivity like freshwater aquifers, glaciers, or dry sandy soils. The objective of the present study was to explore its application for mapping in subsurface agricultural soils to a depth of several meters. For a loamy sand and a clayey site on the North China Plain, clay inclusions in the sand were detected; the thickness, inclination, and continuity of the confining clay and silt layers was assessed; and a local water table was mapped. Direct sampling (soil coring and profiling) in the top meter and independent measurement of the water table were utilized to confirm the findings. Also, effective estimates of the dielectric number for the site with the dielectric number of moist clayey soils depending strongly on frequency were obtained. Thus, important properties of soils, like the arrangement and type of layers and in particular their continuity and inclination, could be explored with moderate efforts for rather large areas to help find optimal locations for the time-consuming and expensive measurements which would be necessary to detail a model of the subsurface.

Effect of Perched Water Tables on Aluminosilicate Stability and Soil Genesis

The mineral stability and solute activities of soil solution extracted from selected horizons of seven studied pedons of Alfisols in Kentucky, USA, and the relationship between distribution of iron-manganese concretions and the restrictive layers were investigated. The results showed that the genesis and development of these soils and mineral weathering trends were strongly influenced by the depth of bedrock and the presence of perched water tables at lithic (limestone) interfaces due to the dissolution and buffering effect of limestone bedrock. The extractable Mg/Ca ratio as depth function and soil depth above bedrock could be used as indices of weathering and degree of soil development. Maximum iron-manganese concretion accumulation was found to occur in the horizon overlying clay horizon (>40% clay) with a sharp increase in clay content (>10%), which suggested that zones of Fe-Mn concretion accumulation in soils of the Inner Bluegrass Region appeared to be a sensitive genetic indicator of argillic horizons with restrictive permeability.

Exploring the groundwater response to rainfall in a translational landslide using the master recession curve method and cross-correlation function

Rainfall is a common trigger for landslide reactivation,as it raises groundwater levels and reduces bedrock or soil shear resistance.This study focuses on the Kualiangzi landslide in the southern region of Sichuan Province,China.Real-time monitoring of groundwater levels and rainfall from July 2013 to September 2016 is analyzed.Groundwater table increments,considering groundwater drainage rate,were calculated using the water-table fluctuation and master recession curve method and the response time of the groundwater table to rainfall events was estimated using the cross-correlation function.Results reveal that groundwater level declines from tension troughs to landslide fronts in the rainy season,with a significant positive correlation between the groundwater level in the tension trough and landslide surface displacement.Evaluated spring elevations for groundwater discharge range from 410 m to 440 m,which is in agreement with the actual spring elevations(390-423 m).Lag times of groundwater response to rainfall decreases with cumulative rainfall of the rainy periods.In the middle part of the landslide,two responses between rainfall and groundwater levels indicate two water movement pathways:Vertical cracks or fractures resulting from the slow landslide movement,and matrix pore space in unconsolidated sediment.Variations in peak values of the cross-correlation function suggest early dominance of the uniform matrix flow and later dominance of preferential flow during the rainy period.

Impact of water table on hierarchically nested groundwater flow system

Water table configuration gives rise to hierarchically nested groundwater flow systems.However,there remains a lack of comprehensive understanding regarding the controlling factors of water table and its impact on flow systems.Moreover,it remains challenging to identify characteristics of water table space variation through limited groundwater observations at the regional scale.Based on two ideal two-dimensional cross-section analytical models,this study presents a simplified approach to preliminarily assess the nonlinear interactions between water table variation and three driving factors:Topography,geol-ogy and climate.Two criteria,C1 and C2,are utilized to address issues at different scales ranging from basin to local:(i)the influence of various factors on water table configuration;and(ii)the influence of water table on groundwater flow pattern.Then,the Ordos Plateau is taken as an example to explore the role of the water table in nested groundwater systems using the provided approach and criterion.The applica-tion of this approach in the Ordos Plateau demonstrates its appropriateness as a practical method for prelim-inarily determining the characteristics of water table configuration and its impact on flow systems.The study explores the mechanism influencing spatial variation in the water table and improves understanding of the interaction between topography,geology,and climate on groundwater flow patterns.

Effect of Irrigation on Groundwater Dynamic Change in the Typical Irrigated Area of Qinghai Province

Under the influence of the natural and human factors, water table of irri- gated area Changes frequently, but it is mainly affected by irrigation water infiltration replenishment during the irrigation. 5 groundwater observation wells were constructed in experimental plot of the Daxia irrigated area to carry out the experiment of the effect of irrigation on groundwater dynamic change in this research. The results showed that the groundwater stage dynarnic change rule of spring and seedling irri- gation stage in the typical plot was fit to the hydrological geology condition of grade- I terrace of Huangshui river valley. On the whole, lateral canal water direction formed a line effect. The No. 1 and No. 2 observation well were the closest to the lateral canal, which received more supplies, and the water level was the highest; the No, 3 observation well took the second place; The No. 4 and No. 5 observation well accepted least supplies, and the water level was the lowest. The rangeability of water table of spring irrigation period was significantly higher than that of seedling irrigation period, this is mainly due to the difference value of intake water volume and drainage water volume of spring irrigation phase was significantly higher than the seedling irrigation phase.

Assessment of deep groundwater over-exploitation in the North China Plain

A series of environmental—geological problems have been caused by over-exploitation of deep groundwater（i.e.,confined aquifer water） in the North China Plain.In order to better understand the status of deep groundwater over-exploitation and the resultant environmental—geological problems on a regional scale,the over-exploitation of groundwater has been assessed by way of the groundwater exploitation potential coefficient（i.e.,the ratio of exploitable amount of deep groundwater to current exploitation）, cumulative land subsidence,and long-term average lowering rate of the groundwater table.There is a good correlation among the results calculated by the different methods.On a regional scale,deep groundwater has been over-exploited and there is no further exploitation potential under the current conditions.The groundwater exploitation degree index takes the exploitation in 2003 as the reference for the calculations, so the results mainly reflect the degree of current groundwater exploitation.The results of over-exploitation of deep groundwater obtained by land subsidence data and long-term average rate of depression of the water table mainly reflect environmental—geological problems caused by exploitation of deep groundwater.

EFFECTS OF WATER TABLE AND NITROGEN ADDITION ON CO_2 EMISSION FROM WETLAND SOIL

Soil respiration is a main dynamic process of carbon cycle in wetland. It is important to contribute to global climate changes. Water table and nutritious availability are significant impact factors to influence responses of CO2 emission from wetland soil to climate changes. Twenty-four wetland soil monoliths at 4 water-table positions and in 3 nitrogen status have been incubated to measure rates of CO2 emission from wetland soils in this study. Three static water-table controls and a fluctuant water-table control, with 3 nitrogen additions in every water-table control, were carried out. In no nitrogen addition treatment, high CO2 emissions were found at a static low water table (Ⅰ) and a fluctuant water table (Ⅳ), averaging 306.7mg/(m2·h) and 307.89mg/(m2·h), respectively, which were 51%-57% higher than that at static high water table (Ⅱ and Ⅲ). After nitrogen addition, however, highest CO2 emission was found at Ⅱ and lowest emission at Ⅲ. The results suggested that nutritious availability of wetland soil might be important to influence the effect of water table on the CO2 emission from the wetland soil. Nitrogen addition led to enhancing CO2 emissions from wetland soil, while the highest emission was found in 1N treatments other than in 2N treatments. In 3 nutritious treatments, low CO2 emissions at high water tables and high CO2 emissions at low water tables were also observed when water table fluctuated. Our results suggested that both water table changes and nutritious imports would effect the CO2 emission from wetland.

The relationship between groundwater and natural vegetation in Qaidam Basin

To accurately evaluate ecological risks trigged by groundwater exploitation,it must be clarified the relationship between vegetation and groundwater.Based on remote sensing data sets MOD13Q1,groundwater table depth(WTD)and total dissolved solids(TDS),the relationship between groundwater and natural vegetation was analyzed statistically in the main plain areas of Qaidam Basin.The results indicate that natural vegetation is groundwater-dependent in areas where WTD is less than 5.5 m and TDS is less than 7.5 g/L.Aquatic vegetation,hygrophytic vegetation and hygrophytic saline-alkali tolerant vegetation are mainly distributed in areas with WTD<1.1 m.Salt-tolerant and mesophytic vegetation mainly occur in areas with WTD of 1.4-3.5 m,while the xerophytic vegetation isprimarily present in areas where WTD ranges from 1.4 m to 5.5 m.Natural vegetation does not necessarily depend on groundwater in areas with WTD>5.5 m.For natural vegetation,the most suitable water TDS is less than 1.5 g/L,the moderately suitable TDS is 1.5-5.0 g/L,the basically suitable TDS is 5.0-7.5 g/L,and the unsuitable TDS is more than 7.5 g/L.

Response of Coastal Groundwater Table to Offshore Storms

Large groundwater table fluctuations were observed in a coastal aquifer during an offshore storm. The storm induced significant changes of the mean shoreline elevation, characterized by a pulse like oscillation. This pulse propagated in the aquifer, resulting in the water table fluctuations. A general analytical solution is derived to quantify this new mechanism of water table fluctuation. The solution is applied to field observations and is found to be able to predict reasonably well the observed storm induced water table fluctuations. Based on the analytical solution, the damping characteristics and phase shift of the oscillation as it propagates inland are examined.

Rise of Urban Water Table as a Cause of Flooding: Improving Knowledge in the City of Niamey (Niger Republic)

Niamey, the capital of Niger, has experienced continuous demographic growth (+4%), accompanied by rapid urban expansion that is insufficiently controlled. This growth, combined with the effects of climate change as well as a drastic change in land use (urbanization of cultivated fields, deforestation of plateaus and erosion of slopes) disrupts the water cycle, thus leading to the superposition of three types of floods: 1) rain floods (monsoon period);2) river floods (Niger river);and 3) flooding caused by rising water table. In several neighbourhoods, the water table is now out in a sustainable manner and degrades already fragile sanitary conditions. This study aims to clarify the functioning of aquifers in the city of Niamey due to the combination of geological, geophysical and hydrogeological data. Hydrogeological investigations make it possible to identify, in areas flooded by the water table, a shallow aquifer with low capacitance (effective porosity of a few %) and low permeability (2 × 10-6 to 1 × 10-4 m/s), overlying at a level shallow clay (~10 m) and lying on the Precambrian base (schists, granites). This configuration limits flows and has led to the appearance of permanent pools created by the water table in the valley thalweg in and around the city. Thus, in Niamey, an increase of up to twenty to forty meters was observed between 1961 and 2021 with seasonal piezometric fluctuations of a pluri-metric order following the rainy season. Beyond the health impacts, this trajectory negatively impacts land and locally causes degradation or displacement of traffic axes. Containing the level of the water table appears to be essential in the long term for sustainable sanitation in the city of Niamey.

Quantification of groundwater recharge and evapotranspiration along a semi-arid wetland transect using diurnal water table fluctuations

Groundwater is a vital water resource in arid and semi-arid areas.Diurnal groundwater table fluctuations are widely used to quantify rainfall recharge and groundwater evapotranspiration(ET_(g)).To assess groundwater resources for sustainable use,we estimated groundwater recharge and ET_(g) using the diurnal water table fluctuations at three sites along a section with different depths to water table(DWT)within a wetland of the Mukai Lake in the Ordos Plateau,Northwest China.The water table level was monitored at an hourly resolution using a Keller DCX-22 A data logger that measured both the total pressure and barometric pressure,so that the effect of barometric pressure could be removed.At this study site,a rapid water table response to rainfall was observed in two shallow wells(i.e.,Obs1 and Obs2),at which diurnal water table fluctuations were also observed over the study period during rainless days,indicating that the main factors influencing water table variation are rainfall and ET_(g).However,at the deep-water table site(Obs3),the groundwater level only reacted to the heaviest rainfalls and showed no diurnal variations.Groundwater recharge and ET_(g) were quantified for the entire hydrological year(June 2017–June 2018)using the water table fluctuation method and the Loheide method,respectively,with depth-dependent specific yields.The results show that the total annual groundwater recharge was approximately 207 mm,accounting for 52%of rainfall at Obs1,while groundwater recharge was approximately 250 and 21 mm at Obs2 and Obs3,accounting for 63%and 5%of rainfall,respectively.In addition,the rates of groundwater recharge were mainly determined by rainfall intensity and DWT.The daily mean ET_(g) at Obs1 and Obs2 over the study period was 4.3 and 2.5 mm,respectively,and the main determining factors were DWT and net radiation.

Responses of phreatophyte transpiration to falling water table in hyper-arid and arid regions,Northwest China

Quantitative assessment of the impact of groundwater depletion on phreatophytes in(hyper-)arid regions is key to sustainable groundwater management.However,a parsimonious model for predicting the response of phreatophytes to a decrease of the water table is lacking.A variable saturated flow model,HYDRUS-1D,was used to numerically assess the influences of depth to the water table(DWT)and mean annual precipitation(MAP)on transpiration of groundwater-dependent vegetation in(hyper-)arid regions of northwest China.An exponential relationship is found for the normalized transpiration(a ratio of transpiration at a certain DWT to transpiration at 1 m depth,T_(a)^(*))with increasing DWT,while a positive linear relationship is identified between T_(a)^(*)and annual precipitation.Sensitivity analysis shows that the model is insensitive to parameters,such as saturated soil hydraulic conductivity and water stress parameters,indicated by an insignificant variation(less than 20%in most cases)under±50%changes of these parameters.Based on these two relationships,a universal model has been developed to predict the response of phreatophyte transpiration to groundwater drawdown for(hyper-)arid regions using MAP only.The estimated T_(a)^(*)from the model is reasonable by comparing with published measured values.

Spatial and temporal variation of groundwater recharge in shallow aquifer in the Thepkasattri of Phuket,Thailand

Whether groundwater resources can be sustainably utilized is largely determined and characterized by hydrogeological parameters.Estimating the groundwater recharge is one of the essential parameters for managing water resources and protecting water resources from contamination.This study researched the spatial and temporal variation of groundwater recharge in the Thepkasattri sub-district through integrating chloride mass balance(CMB)and water table fluctuation(WTF)methods.The chloride content of representative rainfall and groundwater samples was analyzed.Besides,WTF method was adopted from groundwater level data from 2012 to 2015.According to the CMB method,the mean recharge was estimated to be 1172 mm per year,accounting for 47%of the annual rainfall.Moreover,the estimated recharge from the WTF method took 26%of annual rainfall in 2015.The recharge was underestimated according to the WTF method,because of the uncertainty in specific yield estimates and the number of representative wells in the study area.Moreover,the correlation between rainfall and water table fluctuation data indicated the positive linear relationship between two parameters.The spatial recharge prediction indicated that recharge was higher(1200-1400 mm/yr)in the eastern and western catchment,while that in the central floodplains was between 800 mm/yr and 1100 mm/yr.In addition,low recharge value between 450 mm/yr and 800 mm/yr was observed in the south-west part of Thepkasattri.The spatial variation of recharge partly reflects the influences of land use and land cover of the study area.

The response of Caragana microphylla seedlings to water table changes in Horqin Sandy Land,China

This paper focuses on the growth response of Caragana microphylla seedlings to changes of artificially controlled water table in Horqin Sandy Land, China. Monitoring results of soil water content shows that soil moisture is closely correlated to groundwater depths. Soil volumetric water increased rapidly when close to water sources and finally stabilized in a saturated state. The soil moisture trend of CK （control） increased gradually at 0-50 cm of soil depth then decreased to 4% below 50 cm soil depth. C. microphylla can adapt to different soil environments by changes in ecological and physiological characteristics. By comparing the ecological characteristics of C. microphylla seedlings at various water tables, we found that a shallow water table of 40 cm depth inhibited seedling groundwater depth of 120 em was more advantageous for plant growth because of weak ecological characteristics. A height and canopy growth of C. microphylla seedlings. During the first two years, the most suitable water depth for root biomass was 120 cm, and 180 cm for root length. The growth of vertical roots is positively correlated with groundwater depth, and root thickness is the determinate factor for root biomass while the fine root is the determinate factor for root length. A thick root would grow much more in a natural drought environment while access to ground water promotes the growth of fine roots.

Physicochemical and Bacteriological Quality of Ground Water in the Basin of Gounti Yena Valley in Niamey City (Niger Republic)

The Gounti Yéna valley, the subject of this study, is a tributary of the Niger River, it is the main watercourse that divides the left bank of the city of Niamey into two unequal parts. The surface area of its watershed is estimated at about 62 Km2. The objective of the present study is on the one hand to evaluate the current state of the physico-chemical and bacteriological quality of the water of Gounti Yéna basin, and on the other hand to define the risks of water pollution and its origin in the face of the phenomenon of rising water table of this basin. In order to carry out this work, we proceeded to a study of the evolution of the physicochemical and bacteriological parameters of the water of the basin of Gounti Yéna during the period going from November 2020 to October 2021, at the level of four points of sampling chosen from the upstream to the downstream of the basin. The results obtained showed that the physico-chemical quality of the water in Gounti Yéna basin is influenced by the lithology of the watershed, climatic factors (rainfall and temperature) and anthropic actions. This study also highlighted the presence of fecal contamination in the water of the Gounti Yéna basin, with a greater degree of emphasis during the rainy season. This contamination remains a concern and may constitute a health risk.

Numerical Modeling of Shallow Water Table Behavior with Lisse Effect

Air entrapment is an important consideration in environments with shallow water tables and sandy soil, like the condition of highly conductive sandy soils and flat topography in Florida, USA. It causes water table rises in soils, which are significantly faster and higher than those in soils without air entrapment. Two numerical models, Integrated Hydrologic Model (IHM) and HYDRUS-1D (a single-phase, one-dimensional Richards′ equation model) were tested at an area of west central Florida to help further understanding the shallow water table behavior during a long term air entrapment. This investigation employed field data with two modeling approaches to quantify the variation of air pressurization values. It was found that the air pressurization effect was responsible at time up to 40 cm of water table rise being recorded by the observation well for these two models. The values of air pressurization calculated from IHM and HYDRUS-1D match the previously published values. Results also indicated that the two numerical models did not consider air entrapment effect (as the predictive parameters remain uncertain) and thus results of depth to water table from these models did not compare to the observations for these selected periods. Incorporating air entrapment in prediction models is critical to reproduce shallow water table observations.

Dynamics of groundwater recharge near a semi-arid Mediterranean intermittent stream under wet and normal climate conditions

In arid and semi-arid stream-dominated systems,the temporal variability in groundwater recharge has not been widely addressed.Various questions remain about the sources of groundwater recharge,its patterns,and the appropriate measuring techniques.Hence,the main objective of the present study was to assess the changes that might affect the pattern of groundwater recharge under wetter than normal surface water availability.Therefore,the groundwater depth was monitored near a semi-arid Mediterranean intermittent stream on the piedmont of the High Atlas Mountains in the mountain catchment of the Wadi Rheraya over two hydrological years(2014-2016)with different climate conditions:extreme wet and normal conditions.Groundwater recharge was assessed using the episodic master recession algorithm.During the two years,the pattern of groundwater recharge was dominated by episodic events and by a high seasonality from wet seasons to dry seasons.In the wet year(2014-2015),the highest groundwater recharge was recorded following an extreme flood,which deeply replenished groundwater.Furthermore,an exceptional steady state of the groundwater depth was induced by a steady groundwater recharge rate.For several groundwater recharge events,the assessed recharge had multiple sources,mainly from streamflow at the local scale,but possibly from precipitation,underflow,deep percolation or irrigation return from the upstream part of the catchment.Local recharge by streamflow was likely to be short-lived,and lateral recharge was likely to last longer.Consequently,the episodic master recession algorithm estimated the total groundwater recharge that could encompass various sources.In the future,more studies and multidisciplinary approaches should be carried out to partition these sources and determine their specific contributions.In semi-arid stream-dominated systems,different groundwater recharge patterns induced by extreme hydrological events(e.g.,wet events)and various potential sources of groundwater recharge should be considered when assessing and predicting groundwater recharge.

Comparing phreatic evaporation at zero water table depth with water surface evaporation

Salt-affected soils are mostly found in irrigated areas within arid and semi-arid regions where the groundwater table is shallow.Soils of this type have become an increasingly severe problem because they threaten both the environment and the sustainable development of irrigated agriculture.A tool to estimate phreatic evaporation is therefore urgently required to minimize the salinization potential of salt-affected areas.In this context,phreatic evaporation at zero water table depth(E0)is a key parameter for establishing a model for calculating phreatic evaporation.The aim of this study was to explore the law of phreatic evaporation and to develop structurally rational empirical models for calculating phreatic evaporation,based on E0data of six types of soil(i.e.,gravel,fine sand,sandy loam,light loam,medium loam,and heavy loam)observed using the non-weighing lysimeter and water surface evaporation(E601)data observed using a E601 evaporator of same evaporation area with a lysimeter-tube at the groundwater balance station of the Weigan River Management Office in Xinjiang Uygur Autonomous Region,China,during the non-freezing period(April to October)between 1990 and 1994.The relationship between E0and E601was analyzed,the relationship between the ratio of E0to E601and the mechanical compositions of different soils was presented,and the factors influencing E0were discussed.The results of this study reveal that E0is not equal to E601.In fact,only values of the former for fine sand are close to those of the latter.Data also show that E0values are related to soil texture as well as to potential atmospheric evaporation,the ratio of E0to E601and the silt-clay particle content(grain diameter less than 0.02 mm)is negatively exponentially correlated,and that soil thermal capacity plays a key role in phreatic evaporation at E0.The results of this analysis therefore imply that the treatment of zero phreatic depth is an essential requirement when constructing groundwater balance stations to study the law of phreatic evaporation.

Irrigation and Nitrogen Requirements of Wheat under Shallow Water Table Conditions of Asmara, Eritrea

Wheat (Triticum astivum L.) is traditionally rainfed in Eritrea. Yields are low because of poor soil management and low water and nutrient inputs. A field experiment was conducted in Akria farm, located in the outskirts of Asmara. The soil was clay loam associated with non-saline shallow water tables fluctuating from 0.4 to 1.2 m depths during the crop season. Wheat variety Wedel Nile was planted in split plot design with four levels of supplementary irrigations (SI) viz. I1 (rainfed, 0 SI), I2 (1/3 of full SI), I3 (2/3 of full SI), and I4 (full SI) in main plots and three levels of nitrogen viz. N1 (18 kg N haǃ), N2 (50 kg N haǃ), and N3 (100 kg N haǃ) as sub-plots in three replications. Full SI refers to amount of water necessary to replenish soil moisture deficit in the root zone from field capacity to 50% depletion of the available soil moisture. Groundwater table was constant around 0.4 m depth for 32 days from planting and declined slowly thereafter. Wetness around 0.3 m depth was thus near field capacity until second week of December and reduced thereafter with declining water table. Average soil moisture depletion was 94 mm under rainfed and 64 mm under full irrigation. No symptoms of wilting were observed in any of the treatments due to shallow water tables. Upward flux from the water table was 4.6 mm·d-1 until 30 days from planting, which declined to 0.2 mm·d-1 when the water table declined below 0.9 m depth. Optimum yield of wheat (5603 kg·ha-1) was obtained by application of 58 mm irrigation (I3) and 100 kg·ha-1 nitrogen (N3). Total water use for optimum yield of wheat was 382 mm and water use efficiency was 14.7 kg·ha-1·mm-1. Contribution from water table to the evapotranspiration requirements of wheat was highest (61%) under rainfed (I1) and lowest (52%) under full SI (I4).