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Solute transport properties are required to evaluate the risk of contaminating ground water with agricultural chemicals under a wide variety of crop and soil management practices. Most solute transport measurement techniques are tedious and lead to extensive soil excavation. Two experiments were performed to evaluate whether surface transport properties determined by a non-destructive time domain reflectometry (TDR) technique could be used to accurately predict subsurface leaching. TDR probes installed in the surface 2-cm of soil were used to determine resident solute concentration from measured soil surface soil bulk electrical conductivity. Resident concentrations were analyzed with a onedimensional (1-D) solute transport model in order to determine the surface solute transport properties. The surface measurements technique was first tested in a greenhouse soil. Surface dispersivities (1.02 cm) determined by the TDR method were similar to the 30-cm subsurface dispersivities (1.28 cm). The surface solute transport properties were used to predict the chemical concentration distributions within the 30-cm soil layer, and it was found that the centers of mass from predicted and observed subsurface chemical distributions were similar. Further testing of the TDR technique was done in a strip-cropped tile-drained field. The plant-row and interrow zones significantly affected surface and soil profile (120-cm) dispersivities. The soil profile dispersivity (2.68 cm) was larger and more variable than the surface dispersivity (0.91 cm) indicating greater heterogeneity of flow within the soil profile than at the surface. The large soil profile dispersivity indicated that multidimensional flow and lateral spreading occurred in the soil profile. In order to evaluate solute transport in the soil profile, a 1-D convective lognormal transfer (CLT) function model and a 2-D model

Return flows from irrigation form an important component in the overall management of water in a basin. The Nagarjunasagar irrigation project is one of the biggest irrigation projects in India. At the Nagarjunasagar project formulation stage, the return flows were assumed to be 7.5% of the total water drawn into the command area (area irrigated under the canal), which could be approximately 538.08×106 m3. This paper aims to calculate the return flows from the Nagarjunasagar canal command areas. At present, the calculations are made during the period 1982–2004 by using multiple linear regression analysis. Return flows form 15% of the total releases from the canals for the whole study period. During wet, normal, and dry periods, return flows are 29, 20, and 10%, respectively. Similarly, they are 29 and 18% during the kharif (June–October) and rabi (October–February) seasons, respectively.

This document provides an overview of how water resource software’s (WRS) are used to manage water resources issues, criteria for WRS selection, and a high level review of WRS currently available that central and state governments of India can use for water management. The water resource issues covered include water allocation and planning, flood management, groundwater management, conjunctive use, water quality, and sediment transport.

The objective of this study was to investigate the changes in cropland areas as a result of water availability using Moderate Resolution Imaging Spectroradiometer (MODIS) 250 m time-series data and spectral matching techniques (SMTs). The study was conducted in the Krishna River basin in India, a very large river basin with an area of 265 752 km2 (26 575 200 ha), comparing a water-surplus year (2000-2001) and a water-deficit year (2002-2003). The MODIS 250 m time-series data and SMTs were found ideal for agricultural cropland change detection over large areas and provided fuzzy classification accuracies of 61-100% for various land-use classes and 61-81% for the rain-fed and irrigated classes. The most mixing change occurred between rain-fed cropland areas and informally irrigated (e.g. groundwater and small reservoir) areas. Hence separation of these two classes was the most difficult. The MODIS 250 m-derived irrigated cropland areas for the districts were highly correlated with the Indian Bureau of Statistics data, with R2-values between 0.82 and 0.86. The change in the net area irrigated was modest, with an irrigated area of 8 669 881 ha during the water-surplus year, as compared with 7 718 900 ha during the water-deficit year. However, this is quite misleading as most of the major changes occurred in cropping intensity, such as changing from higher intensity to lower intensity (e.g. from double crop to single crop). The changes in cropping intensity of the agricultural cropland areas that took place in the water-deficit year (2002-2003) when compared with the water-surplus year (2000-2001) in the Krishna basin were: (a) 1 078 564 ha changed from double crop to single crop, (b) 1 461 177 ha changed from continuous crop to single crop, (c) 704 172 ha changed from irrigated single crop to fallow and (d) 1 314 522 ha changed from minor irrigation (e.g. tanks, small reservoirs) to rain-fed. These are highly significant changes that will have strong impact on food security. Such changes may be expected all over the world in a changing climate.

To keep pace with population and economic growth, the city of Hyderabad, India, will need to identify and develop new supply sources almost continually. Increasing population growth rate, declining surface water resources, overexploitation of groundwater, deterioration of ground water quality and poor sewage treatment are the major water-related issues in Hyderabad. This paper reviews the current situation facing policy makers who need to come to terms with the problem of restricted water supply and increasing demand in an urban centre such as Hyderabad, India. The City Water Balance model developed in this study can be used to analyse different scenarios that include water conservation, urban wastewater reuse and improvement of distribution and conveyance efficiency. Water conservation programs, which include a 5% conveyance efficiency improvement, reusing 90 million cubic metres (MCM) of urban runoff and adoption of water harvesting by 0.5 million households together with recycling 120 MCM of wastewater recycling wastewater would be sufficient to meet the water demand by 2031, if the population grows at a rate of 2.5%.

In many river basins, upstream development and interannual variations in rainfall can cause both episodic and chronic shortages in water supplies downstream. Continued rapid development of surface and groundwater throughout the Krishna Basin in southern India resulted in historically low inflows to the main canals of the Nagarjuna Sagar irrigation project 8,955 km 2 during a recent drought 2002-2004. This paper presents an integrated approach to assess how cropping patterns and the spatial equity of canal flow changed with water supply shocks in the left canal command area 3,592 km 2 of Nagarjuna Sagar. We combined 3 years 2000-2003 of canal release data with census statistics and high temporal resolution 8-10 days moderate resolution imaging spectrometer MODIS 500-m resolution satellite imagery. The impact of water scarcity on land use pattern, delineated by MODIS images with moderate spatial resolution, was comparable with the census statistics, while the MODIS data also identified areas with changes and delays in the rice crop area, which is critical in assessing the impact of canal operations. A 60% reduction in water availability during the drought resulted in 40% land being fallowed in the left-bank canal command area. The results suggest that head reach areas receiving high supply rates during a normal year experienced the highest risks of fluctuations in water supply and cropped area during a water short year compared to downstream areas, which had chronically low water supply, and better adaptive responses by farmers. Contrary to expectations, the spatial distribution of canal flows among the three major zones of the command area was more equitable during low-flow years due to decreased flow at the head reach of the canal and relatively smaller decreases in tail-end areas. The findings suggested that equitable allocations could be achieved by improving the water distribution efficiency of the canal network during normal years and by crop diversification and introduction of alternative water sources during water shortage years. The study identified areas susceptible to decreases in water supplies by using modern techniques, which can help in decision-making processes for equitable water allocation and distribution and in devel- oping strategies to mitigate the effects of water supply shocks on cropping patterns and rural livelihoods.

The combined use of remote sensing and a distributed hydrological model have demonstrated the improved understanding of the entire water balance in an area where data are scarcely available. Water use and crop water productivity were assessed in the Upper Bhima catchment in southern India using an innovative integration of remotely sensed evapotranspiration and a process-based hydrological model. The remote sensing based Surface Energy Balance Algorithm for Land (SEBAL) was used to derive an 8 month time series of observed actual evapotranspiration from October 2004 to May 2005. This dataset was then used in the calibration of the Soil and Water Assessment Tool (SWAT). This hydrological model was calibrated by changing 34 parameters to minimize the difference between simulated and observed actual evapotranspiration. The calibration efficiency was assessed with four different performance indicators. The calibrated model was used to derive a monthly basin water balance and to assess crop water productivity and crop water use for the irrigation year 2004–2005. It was found that evapotranspiration is the largest water loss in the catchment and total evaporative depletion was 38,172 Mm3 (835 mm). Of the total evaporative depletion 42% can be considered as non-beneficial and could be diverted to other beneficial utilization. Simulated crop water productivities for sugarcane, sorghum and winter wheat are relatively high at 2.9 kg/m3, 1.3 kg/m3 and 1.3 kg/m3, respectively. The frequency distributions of crop water productivity are characterised by low coefficient of variation, yielding limited scope for improvement in the agricultural areas under the current cropping systems. Further improvements in water productivity may however be achieved by shifting the crop base from sugarcane to a dual crop and introducing a fallow period from March to May or by converting non-productive rangelands to bio fuel production or other agricultural land uses.

Although nmnerous studies have investigated the effects of crop production practices on soil water dynamics, not much information is available on the impact of row position on solute transport. A field experiment was carried out to evaluate surface and subsurface solute transport properties in plant row, nontrafficked interrow, and trafficked interrow positions. For this purpose, a plot of 14 X 14 m in a strip­ cropped field with soybean (Glycine max L. Merr), corn (Zea mays L.), and oat (Avena L.) was selected. Mter harvesting the crops, surface (top 2 cm) electrical conductivity measurements were made by time domain reflectometry at 45 locations during a cWoride pulse leaching experiment. At the conclusion of the pulse leaching experiment, 120-cm deep soil cores were collected at the 45 locations to measure the soil profile chemical distributions. No crop or row position effects were observed for surface-determined pore water velocities (v), whereas profile-determined v was greater in plant row versus interrow positions when averaged over all crops. Overall, the profile-determined v was slightly greater than the surface determined v, probably because of lower effective or mobile water contents. The profile-determined dispersion coefficient (D) was smaller in row positions than interrow positions in soybean and corn, perhaps because ofsurface ponding in the interrow positions ofthe crops resulting in macropore flow. Profile-determined D was greater in the interrow positions of soybean than oat, again reflecting possible macro­ pore flow. Overall, the mean soil profile dispersivity (A = 2.97 cm) was larger than the surface soil (A = 1.02 cm). The local surface solute transport varied by row positions, whereas profile solute transport was affected by both row position and crop, perhaps due to surface ponding producing macropore flow in the trafficked and nontrafficked interrows ofsoybean and the trafficked interrows ofcorn. Thus, a one-dimensional solute transport model with a spatially distributed flux or potential controlled upper boundary condition must be used to model this system. (Soil Science 2007;172:419-431)

Management of chemicals in soil is important, yet the complexity of field soils limits prediction of management effects on transport. To date, few methods have been available for field measurement of chemical transport properties, but a recently developed dripper-time domain reflectometry technique allows rapid collection of data for determining these properties. The objective of this work was to apply this technique for comparison of chemical transport properties for different soil management zones. Experiments were conducted comparing four interrow management zones: no-till nontrafficked, no-till trafficked, chisel plow nontrafficked, and chisel plow trafficked. Drip emitters were positioned at 12 locations in each zone and used to apply water followed by a step input of CaCl 2 tracer solution. Breakthrough curves were measured via electrical conductivity with time domain reflectometry probes. The mobile-immobile model was fit to the breakthrough curves to determine chemical transport properties. Mean chemical transport properties were 0.34, 0.1 h -1 , 10 cm h -1 , 164 cm 2 h -1 , and 5 cm, for the immobile water fraction, mass exchange coefficient, average pore-water velocity, mobile dispersion coefficient, and dispersivity, respectively. All five properties showed significant differences between management zones. Differences in mass exchange and mobile dispersion coefficients coincided with differences in tillage, while differences in mean pore water velocities coincided with differences in traffic. The immobile water fraction was largest for the no-till nontrafficked zone. These results represent one of very few reports for field measurement of chemical transport properties and the first application of this approach for comparison of chemical transport properties across management zones.

Most solute transport measurement techniques are tedious and require extensive soil excavation. A field experiment was conducted to evaluate whether surface transport properties determined by a nondestructive time domain reflectometry (TDR) technique could be used to accurately predict tile flux concentrations. A 14 by 14 m field plot selected above a 1.1-m deep tile drain was studied. Low electrical conductivity (EC) water was sprinkled on the plot surface, and after reaching a steady-state condition, a pulse of calcium chloride solution (16.3 cm) with an EC of 23 dS m -1 was applied through the same sprinklers. Time domain reflectometry equipment was used to record the change in EC of surface (∼ top 2 cm) soil at 45 locations. The EC of the tile drainage flow was measured continuously with an EC probe. The surface convective lognormal transfer (CLT) function parameters, log mean irrigation depth, μ I , and its standard deviation, σ I , were found to be 3.44 and 0.94 [ln(cm)], respectively, for a reference depth of 110 cm. These surface parameters were used in a one-dimensional (1-D) CLT model and in a two-dimensional (2-D) model (CLT vertical function combined with exponential horizontal transfer function) to predict the tile flux concentrations. The 1-D CLT model predicted an earlier arrival time of chemicals to the tile drain than observed values. The root mean square error, RMSE, of the 1-D CLT predictions was 0.123, and the coefficient of efficiency, E, was -0.47. The 2-D model predictions of tile flux concentrations were similar to the observed values. The root mean squared errors (RMSE) and E were 0.023 and 0.94, respectively. The findings suggest that in this field soil, the surface solute transport properties determined by TDR could be combined with a 2-D transport model to make reasonable predictions of tile flux concentrations.

Field determined hydraulic and chemical transport properties can be useful for the protection of groundwater resources from land-applied chemicals. Most field methods to determine flow and transport parameters are either time or energy consuming and/or they provide a single measurement for a given time period. In this study, we present a dripper-TDR field method that allows measurement of hydraulic conductivity and chemical transport parameters at multiple field locations within a short time period. Specifically, the dripper-TDR determines saturated hydraulic conductivity (Ks), macroscopic capillary length (λc), immobile water fraction (θim/θ), mass exchange coefficient (α) and dispersion coefficient (Dm). Multiple dripper lines were positioned over five crop rows in a field. Background and step solutions were applied through drippers to determine surface hydraulic conductivity parameters at 44 locations and surface transport properties at 38 locations. The hydraulic conductivity parameters (Ks, λc) were determined by application of three discharge rates from the drippers and measurements of the resultant steady-state flux densities at the soil surface beneath each dripper. Time domain reflectometry (TDR) was used to measure the bulk electrical conductivity of the soil during steady infiltration of a salt solution. Breakthrough curves (BTCs) for all sites were determined from the TDR measurements. The Ks and λc values were found to be lognormally distributed with average values of 31.4 cm h−1 and 6.0 cm, respectively. BTC analysis produced chemical properties, θim/θ, α, and Dm with average values of 0.23, 0.0036 h−1, and 1220 cm2 h−1, respectively. The estimated values of the flow and transport parameters were found to be within the ranges of values reported by previous studies conducted at nearby field locations. The dripper TDR method is a rapid and useful technique for in situ measurements of hydraulic conductivity and solute transport properties. The measurements reported in this study give clear evidence to the occurrence of non-equilibrium water and chemical movement in surface soil. The method allows for quantification of non-equilibrium model parameters and preferential flow. Quantifying the parameters is a necessary step toward determining the influences of surface properties on infiltration, runoff, and vadose zone transport.

Hydraulic and chemical transport properties are the major inputs in predictive models that simulate the movement of water and chemicals through the vadose zone. However, there is a lack of field measurements of such properties to verify models describing water and chemical movement through the soil. One of the objectives of this study was to use a point source method to determine simultaneously the hydraulic and chemical transport properties at multiple field locations. A second objective was to determine the spatial distribution of such properties across a field. A total of 50 field locations within a 7 × 15-m area were rapidly and simultaneously evaluated for such properties. The hydraulic properties were the saturated hydraulic conductivity (K s ) and the macroscopic capillary length (λ c ). The chemical transport properties were the immobile water content, expressed as a fraction of water content (θ im /θ) and the mass exchange coefficient (a). The hydraulic properties were determined by applying three discharge rates from irrigation dripper lines and measuring the resultant steady-state flux densities at the soil surface beneath each emitter. The chemical transport properties were determined by applying a sequence of three conservative tracers at a steady-state infiltration rate and measuring their resident concentration in the soil. The K s values ranged from 7.5 to 79.0 cm h -1 , with a median of 27.4 cm h -1 (± 16.8). The λ c values ranged from 0.03 to 13.1 cm, with a median of 2.6 cm (± 3.6). The θ im /θ values ranged from 0.36 to 0.88, with a median of 0.57 (± 0.098). The a values ranged from 0.002 to 0.12 h -1 , with a median of0.034 h -1 (± 0.027). The values of the hydraulic and chemical transport parameters were found to be comparable with values reported by studies conducted on nearby field locations on similar soil. Based on semi-variogram analysis, the measured properties were not spatially correlated. Because the method required only 2 days to collect data it should prove useful for future studies that require extensive field measurements of hydraulic and chemical transport properties.

[1] Changes in both land cover and the atmosphere have impacted the heat fluxes of south Asia in ways that may have altered the timing and magnitude of the monsoon. Century-long budgets of water and energy in the Krishna Basin (258,948 km2) in southern India demonstrate that irrigation impacted the sensible heat flux of the land surface (H) as much as or more than did the atmospheric brown cloud (ABC) over 1960–2005. Annual discharge of the Krishna River fell from 226 mm during pre-irrigation land cover (1901–1960) to 64 mm by 1990–2005, when 14–20% of the basin area was irrigated. Over the same period, annual evaporation increased by 166 ± 32 mm (+28%) causing H to decrease by 12.7 ± 2 W m−2 (−18%) compared to a decrease of 11.2 ± 1.8 W m−2 caused by the atmospheric brown cloud (ABC). The rate of change in H during irrigation expansion (1960–1990) was between −3.4 and −5.0 W m−2 per decade (da−1) due to irrigation expansion and −1.8 to −2.3 W m−2 da−1 due to the ABC. The trend in H caused by irrigation was negligible over 1990–2005 as irrigated area and evaporation stabilized. Previous work using the Parallel Climate Model estimated that the ABC decreased the latent heat flux by 2.4 W m−2; this decrease was more than offset by irrigation, resulting in a net increase in the latent heat flux of 12.9 W m−2. The maximum surface air temperature (Tmax) either decreased or remained the same in areas experiencing irrigation expansion but increased in a majority of unirrigated areas during the post-monsoon season. The results provide observational evidence that irrigation changed both the basin-scale sensible heat flux and surface air temperatures.

Chemicals that leach through soil pose threats to surface and groundwater quality. It is difficult and expensive to measure subsurface chemical transport and the transport properties required for extrapolating predictions beyond limited observations. The objective of our study was to evaluate whether solute transport properties measured at the soil surface could be used to predict subsurface chemical movement. The study was conducted in a greenhouse soil pit. The solute transport properties of the surface 2-cm soil layer were determined by using time domain reflectometry (TDR) to measure the bulk electrical conductivity during a step application of CaCl2 solution. The movement of chemicals in the subsurface was measured within the top 30 cm of soil following a pulse input of CaCl2 solution. A comparison of the measured chemical transport properties in the surface and subsurface zones of the soil showed that the parameters were similar. Furthermore, the estimated parameters determined by the surface TDR method were used to predict the chemical concentration distributions within the 30-cm soil layer, and it was found that the centers of mass of predicted chemical distributions were not significantly different from the measured ones. Therefore, the surface TDR measurements could be used to successfully predict subsurface chemical transport within the upper 30 cm of the soil. This surface measurement technique is a promising tool for vadose zone chemical transport studies.