Seepage Losses Research Articles

English

This study was carried out to establish farmers’ perceptions regarding low agricultural productivity and to document their ideas for improving the performance of agriculture sector in South Sudan. The results reveal that the major challenges related to low agricultural productivity as perceived by farmers include poor leveling of fields, poor irrigation management, low water availability, loss of land due to salinity and low water use efficiency due to seepage and runoff losses. Low water availability is considered as the biggest challenge for improving agricultural productivity because dependence on seasonal rain results in low crop yields and serious food shortages during most part of a year. Therefore, installation of public wells to increase groundwater availability for irrigation and establishment of rainwater harvesting structures are proposed as the potential solutions to solve irrigation water problems and overcome food shortages. Strengthening of extension services and training of vegetable growers on drip and sprinkler irrigation system along with the provision of irrigation equipment can help a great deal in increasing agricultural productivity. The state and national governments should provide high quality seeds and loans to the vegetable growers to enable them improve their crop production and cultivation of crops during the dry periods. Key words: Agricultural productivity, irrigation management, food security, livelihood, poverty.

Using data mining to stop or mitigate lost circulation

Lost circulation materials (LCMs) are available in a great variety of materials, sizes, and can vary in the method of application. Selecting the right LCM and treatment for the job is critical in achieving the successful control of the lost circulation event.After reading a good number of papers and case histories regarding lost circulation materials and treatments and comparing the current classification to actual real field data, a large gap was found in the current calcification of lost circulation materials and treatments. An updated classification of lost circulation materials and treatments was provided based on the type of losses and applications.Data were collected on both LCM and applications from various number of sources in the Basra area of Iraq where drilling operations are highly susceptible to lost circulation in the Dammam, Hartha and Shuaiba formations. After analyzing the data, the best lost circulation treatments and materials to treat seepage, partial, severe, and complete losses in Basra oil fields were provided as a flowchart accomplished by practical guidelines that can serve as a reference material for the drilling personnel when responding to lost circulation in the field.This paper will also discuss methods that are used to ameliorate lost circulation without the use of traditional lost circulation materials. Example of the alternative approaches include discussions of blind drilling and floating mud cap drilling using case histories from the Basra fields.The results of this analysis provide a path forward for effectively and systematically using lost circulation materials and treatments in the Basra area. The methodologies presented in this work can be adapted and used to treat lost circulation worldwide.

Combining imaging techniques with nonparametric modelling to predict seepage hotspots in irrigation channels

Using the Murrumbidgee Irrigation Area, Australia as a case study, we present an integrated approach for identifying seepage hotspots and predicting seepage losses from open channel. The approach is particularly important to facilitate investments for improving irrigation conveyance efficiencies, thus enabling sustainable agricultural water use. A qualitative assessment is used for capturing seepage hotspots with electromagnetic inductance (EM31) imaging techniques, followed by actual seepage measurements. Based on data from major irrigation systems in the southern Murrumbidgee Irrigation Area, a case is made for cost-effective methodology to locate seepage hotspots and quantify seepage losses in channels. In particular, a predictive model was developed based on EM31 survey and direct measured channel seepage data. The main input data for the model were EM values, soil types, water depth in channels, wetted perimeter of channels and whether water is flowing in channels. The output from the model was a seepage loss value in channels. The three different modelling techniques considered were the Generalised Linear Mixed (GLM) model, Random Forest (RF) model and Generalized Boosted Regression Model (GBM), and a best performing model for seepage prediction was identified. The RF model was found to the most reliable, explaining 60% of the variability in the data and with the least mean absolute error. The study indicated that the RF model can be used to locate seepage hotspots in channels and determine the magnitude of seepage losses.

Utilizing non-traditional data sources for estimating channel seepage losses

Accurate streamflow data, which constitute the basic component in estimating seepage losses or gains in streamflow are in short supply in developing countries. The lack of either financial or technical resources, or both, and at times, the lack of understanding of the importance of accurate streamflow measurements in supporting modeling and water resources decision making process hinder the installation and proper maintenance of streamflow gauges. Therefore, the current study adopted the aim of demonstrating the feasibility of utilizing alternative streamflow data sources in hydrologic studies. In the current study, such sources included effluent from a large wastewater treatment plant as an inflow to the river segment under consideration while the outflow from the same river segment was taken to be the flow discharged into a dam reservoir as calculated from daily dam reservoir water balance. A water balance was established for a 48 km segment on the Zarqa River in Jordan with components covering the inputs of discharge from springs, and wastewater treatment plants and outputs such as direct evaporation, and surface withdrawals for irrigation purposes. Channel seepage was estimated as the difference between inputs and outputs of the river segment water balance. Final results demonstrated the feasibility of utilizing non-traditional data sources, whenever available, to conduct analysis that traditionally has not been possible.

Arsenic and other water‐quality issues affecting groundwater, Indus alluvial plain, Pakistan

AbstractGroundwater beneath the alluvial plain of the Indus River, Pakistan, is reported to be widely polluted by arsenic (As) and to adversely affect human health. In 79 groundwaters reported here from the lower Indus River plain in southern Sindh Province, concentrations of As exceeded the WHO guideline value for drinking water of 10 μg/L in 38%, with 22% exceeding 50 μg/L, Pakistan's guideline value. The As pollution is caused by microbially‐mediated reductive dissolution of sedimentary iron oxyhydroxides in anoxic groundwaters; oxic groundwaters contain <10 μg/L of As. In the upper Indus River plain, in Punjab Province, localized As pollution of groundwater occurs by alkali desorption as a consequence of ion exchange in groundwater, possibly supplemented by the use for irrigation of groundwater that has suffered ion exchange in the aquifer and so has values >0 for residual sodium carbonate. In the field area in southern Sindh, concentrations of Mn in groundwater exceed 0.4 mg/L in 11% of groundwaters, with a maximum of 0.7 mg/L, as a result of reduction of sedimentary manganese oxides. Other trace elements pose little or no threat to human health. Salinities in groundwaters range from fresh to saline (electrical conductivity up to 6 mS/cm). High salinities result from local inputs of waste water from unsewered sanitation but mainly from evaporation/evapotranspiration of canal water and groundwater used for irrigation. The process does not concentrate As in the groundwater owing to sorption of As to soils. Ion exchange exerts a control on concentrations of Na, Ca, and B but not directly on As. High values of Cl/Br mass ratios (most ≫288, the marine value) reflect the pervasive influence on groundwater of sewage‐contaminated water from irrigation canals through seepage loss and deep percolation of irrigation water, with additional, well‐specific, contributions from unsewered sanitation.

A modeling approach to establish environmental flow threshold in ungauged semidiurnal tidal river

Due to shortage of flow monitoring data in ungauged semidiurnal river, ‘environmental flow’ (EF) determination based on its key component ‘minimum low flow’ is always difficult. For EF assessment this study selected a reach immediately after the Halda-Karnafuli confluence, a unique breeding ground for Indian Carp fishes of Bangladesh. As part of an ungauged tidal river, EF threshold establishment faces challenges in changing ecological paradigms with periodic change of tides and hydrologic alterations. This study describes a novel approach through modeling framework comprising hydrological, hydrodynamic and habitat simulation model. The EF establishment was conceptualized according to the hydrologic process of an ungauged semi-diurnal tidal regime in four steps. Initially, a hydrologic model coupled with a hydrodynamic model to simulate flow considering land use changes effect on streamflow, seepage loss of channel, friction dominated tidal decay as well as lack of long term flow characteristics. Secondly, to define hydraulic habitat feature, a statistical analysis on derived flow data was performed to identify ‘habitat suitability’. Thirdly, to observe the ecological habitat behavior based on the identified hydrologic alteration, hydraulic habitat features were investigated. Finally, based on the combined habitat suitability index flow alteration and ecological response relationship was established. Then, the obtained EF provides a set of low flow indices of desired regime and thus the obtained discharge against maximum Weighted Usable Area (WUA) was defined as EF threshold for the selected reach. A suitable EF regime condition was obtained within flow range 25–30.1 m3/s i.e., around 10–12% of the mean annual runoff of 245 m3/s and these findings are within researchers’ recommendation of minimum flow requirement. Additionally it was observed that tidal characteristics are dominant process in semi-diurnal regime. However, during the study period (2010–2015) the validated model with those reported observations can provide guidance for the decision support system (DSS) to maintain EF range in an ungauged tidal river.

Impacts of off-farm employment on groundwater irrigation in North China

AbstractThis study examines the relationship between groundwater irrigation and off-farm employment with a set of household level data collected in North China. The results provide evidence that off-farm employment reduces both time spent on irrigation in terms of total hours of irrigation and the amount of groundwater pumped. However, these effects have not resulted in losses of crop production. In fact, water productivity measured as output value produced per m3of groundwater pumped is higher among households with off-farm employment. These seemingly contradictory findings are explained by the increased use of water-saving technologies such as furrow irrigation, underground pipes and/or lined canals. These technologies reduce seepage losses during the conveyance of groundwater as well as during irrigation of the fields. As a result, less groundwater needs to be pumped to achieve the same level of groundwater irrigation application rate in the field.

Modeling the impact of aquifer recharge, in-stream water savings, and canal lining on water resources in the Walla Walla Basin

The Walla Walla Basin in Eastern Oregon and Washington, USA, faces challenges in sustaining agricultural water supplies and endangered fisheries in the Walla Walla River (WWR). 11.1 Mm3/year of managed aquifer recharge (MAR) is currently used in the basin to supplement groundwater with the goal of maximizing instream flow during dry summer months. A numerical groundwater–surface water model was calibrated to observed hydrological conditions and applied to predict future conditions under current management practices (baseline model) and for four alternative water management scenarios. These scenarios were developed to predict how lining canals to eliminate seepage losses and concurrently reducing irrigation diversions from the WWR will impact stream flows and groundwater storage with varying levels of MAR. Model results predict that seasonal low flows in the WWR at the downstream reference location will increase an average of 0.13 m3/s relative to baseline conditions due to instream water savings with conversion of unlined canals to pipelines (Current MAR-Piped). With MAR increased to 18.0 and 29.9 Mm3/year and an additional 58 km piping (Increased MAR-Piped and Maximum MAR-Piped scenarios), the predicted flow increases in the WWR-averaged 0.16 and 0.26 m3/s, respectively. Without MAR (No MAR-Piped), flow is predicted to decrease for the months of August and September relative to baseline conditions. The “No MAR-Piped” and “Current MAR-Piped” scenarios are predicted to reduce groundwater storage relative to the baseline model due to reduced canal seepage. The “Maximum MAR-Piped” scenario is predicted to yield groundwater storage that is greater than baseline conditions, while groundwater storage is predicted to be similar to baseline conditions in the “Increased MAR-Piped” scenario. Model results indicate that canal piping in combination with increased MAR can allow for increased summer flows in the WWR while stabilizing groundwater storage levels for agricultural use and ecological benefits; whereas lining canals without MAR would be detrimental to environmental flows in the WWR and its tributaries.

Estimation of Seepage Loss in Irrigation Canals of Tendaho Sugar Estate, Ethiopia

Open canals are the common method used to convey water for irrigation in Ethiopian sugar estate, however, little or no attention is given to the evaluation of conveyance systems. Consequently, many of the existing conveyance systems are deteriorating in their physical structures, operation and management. Due to this the current study was conducted to quantify the amount of seepage loss through lined and unlined irrigation canals of Tendaho sugar estate. Seepage losses were determined by inflow-out flow method for primary, secondary, and tertiary canals, while water velocity was determined using a current-meter. The average seepage losses were resulted in 0.55% per 100 m (0.0126 lit/s/m2) and 0.84% per 100 m (0.0180 lit/s/m2) for lined and unlined primary canals whereas, 3.65% per 100 m (0.0391 lit/s/m2) and 4.27% per 100 m (0.0248 lit/s/m2) were obtained for secondary and tertiary canals, respectively. In the result, primary canal seepage loss was higher in unlined than in lined by 0.0054 lit/s/m2 of wetted area of the canal. The result reveals that high seepage loss for both lined and unlined canals may be attributed through damage of geomembrane lining and poor maintenance of earthen canals. To minimize excess seepage and improve the conveyance system, overall maintenance and repair of canals should be done in the Estate.

Practical Strategies and Engineered Solutions to Minimize the Impact of Lost Circulation Problem

Lost circulation is a complicated problem to be banned or combatted during the drilling operations. Mud losses remedies are extensively used to stop or mitigate losses using remedial methods or to prevent mud losses using proactive measures. Lost circulation presents a lot of big challenges during drilling. To address these problems, a number of methods/techniques have evolved over the years. The Rumaila field in Iraq is one of the largest oilfields in the world. Wells drilled in this field are highly susceptible to lost circulation problems when drilling through the Hartha formation. Lost circulation events range from seepage losses to complete loss of the borehole and are a critical issue in field development. This paper describes a study of the lost circulation events for more than 300 wells drilled in the Rumaila field. Lost circulation events were extracted from daily drilling reports, final drilling reports, and technical reports. Key drilling parameters (e.g. ROP, SPM, RPM, WOB, bit type) and mud properties (e.g. mud weight, yield point, gel strength) at the time of each event were recorded along with the lost circulation remedies attempted, and the outcome of those remedies. These data have been analyzed to determine the best ranges of the key drilling parameters that have the greatest chance of mitigating lost circulation in the Hartha formation. Practical field information from the Rumaila field and range of sources have been reviewed and summarized to develop an integrated methodology and flowchart for handling lost circulation events in this formation. In a related development, this paper will be extended work along with previous comprehensive statistical study and sensitivity analysis models about the Hartha formation to obtain the best field procedures for avoiding or minimizing lost circulation events in the Hartha formation. Proactive approaches have been made prior entering the Hartha formation to prevent or mitigate the occurrence of lost circulation. A unique statistical work, primitive mechanisms, typical drilling fluid properties and recommended operational drilling parameters have been evaluated to use during drilling the Hartha formation. In addition, corrective actions have been determined for each kind of the mud losses to provide effective remedies, minimize non-productive time, and reduce cost. Lost circulation strategy to the Hartha formation has been summarized depending on statistical work and economic analysis evaluation to determine the most successful remedies for each type of the losses. These treatments are classified by relying on the mud losses classifications in order to avoid unwanted consequences due to inappropriate actions. This study provides a typical compilation of information regarding traditional approaches and the latest approaches to lost circulation control. In addition, the work attempts to provide useful guidelines or references for both situations in terms preventive measures, remedial methods, and analytical economic study.

Behavior of fiber reinforced concrete for controlling the rate of cracking in canal-lining

Seepage is a major water loss (20–30%) from the canal as compared to the other forms of water losses. Concrete is commonly used for canal-lining to reduce the seepage loss. Considerable seepage (15–20%) has been observed even in the cement–concrete conventional sections. The performance of canals decreases with an increase in the rate of cracking in concrete canal-lining. The rate of cracking in canal-lining can be reduced by improving the flexure, compressive, and splitting-tensile strengths of concrete. Out of these, splitting-tensile strength of concrete plays a vital role in controlling cracks. The use of fibers for characteristics improvement of concrete is very ancient. Natural fibers include many benefits, like low cost due to its abundance, least health hazards, and flexibility. The use of synthetic fibers as reinforcement in matrix has also attained intentness by reasons of its high strength, less water absorption, and low density in nature. The overall aim of the research program is to explore materials for better performance of canal-lining in terms of reduced water losses by controlling its rate of cracking due to alternate wetting and drying, and due to differential settlement, etc. The purpose of this work is to examine experimental behaviors of jute fiber reinforced concrete (JFRC), nylon fiber reinforced concrete (NFRC), and polypropylene fiber reinforced concrete (PPFRC) for controlling the rate of cracking in canal-lining. For this purpose, the mechanical properties (compressive, splitting-tensile, and flexure strengths, energies, and toughness indices), water absorption, and linear shrinkage of JFRC, NFRC, and PPFRC are determined experimentally as per ASTM standards. The properties of plain concrete (PC) are used as reference. The proportion of 1:3:1.5:0.7 (cement: sand: aggregate: water) is used for PC mix. The mixes of JFRC, NFRC, and PPFRC are manufactured by adding the jute fibers, nylon fibers, and polypropylene fibers, respectively, in the same mix design as that of PC. For production of each type of fiber reinforced composite (FRC), fibers having length of 50mm are added in concrete by an amount of 5% (by mass of cement). A reduction in compressive properties, and an improvement in splitting-tensile and flexural strengths, water absorption and linear shrinkage is exhibited by FRCs over that of PC. Among the tested FRCs, PPFRC shows better performance. This may ensure to control the rate of cracking in canal-lining, ultimately improving its performance.

Effects of various shrimp (Penaeus monodon) densities on their growth, water and sediment quality, and water budget

The total water use (TWU) and consumptive water use index (CWUI) in monoculture of Penaeus monodon under varying intensity levels [T1: 150,000 post larvae (PL) ha−1, T2: 200,000 PL ha−1, T3: 250,000 PL ha−1] were quantified. Treatment-wise-estimated TWU was 2.98 × 104, 3.24 × 104, and 3.59 × 104 m3 ha−1 125d−1, while the CWUI was 5.12, 4.72, and 4.96 m3 kg−1 shrimp production in T1, T2, and T3, respectively. The estimated evaporation and seepage loss ranged between 1.2–1.7 and 1.1–1.5 m3 water kg−1 shrimp production, respectively, and contributed significantly to consumptive water use (CWU). Higher the stocking density, lower was the water quality suitability index (WQSI) as in T3 followed by T2 and T1. WQSI up to 75 days of culture rated very good, ranged between 7.5–9.0 in T1 and T2, while rest of the period it was good (5.5–7.5) with moderate management requirements. Treatment-wise sediment load ranged between 39.0 and 45.3 m3 t−1 shrimp biomass. Among the treatments, minimization of total water use (3.24 × 104, m3), CWU (2.16 × 104, m3) and water exchange (0.90 × 104, m3) at stocking density 20 post-larvae m−2 (T2), resulted in higher (p < 0.05) growth rate (30.45 g), yield (4.58 t ha−1), output value - cost of cultivation ratio (2.46) and net consumptive water productivity (USD 0.65 m−3). Findings of this study would help in preventing wasteful use of water and would address the management and operational issues in coastal shrimp aquaculture.

Antiflotation design for water tank using pressure relief technique

ABSTRACTA pressure relief technique has been proposed to reduce hydrostatic pressures by opening drainage holes around a water tank. This solution is evaluated by laboratory experiments and numerical parametric investigation. After seepage flow is allowed, the hydraulic head acting on the water tank is reduced due to seepage losses. The drainage holes should be opened on the base slab near the sidewalls, and at a certain height on the sidewalls. Given a fixed total opening area, the number of drainage holes with smaller diameter should be allowed near the edge of the water tank to increase the efficacy of the approach. The properties of the surrounding soil influence the results significantly, where a cushion layer with a higher hydraulic conductivity and a greater thickness is beneficial to the stability of the water tank, and a backfill layer with adequate thickness and hydraulic conductivity should be selected. An illustrative example is given in the end to demonstrate the advantage of the proposed antiflotation design strategy compared to the conventional enhanced self-weight method, and more economic design using less reinforcement and concrete can be achieved.

An overview of hydro-sedimentological characteristics of intermittent rivers in Kabul region of Kabul river basin

ABSTRACTIntermittent rivers are defined as rivers with a high seasonality in water, sediment transport and habitat. In this study, an attempt is made to outline the major hydro-sedimentological characteristics of intermittent rivers systems using the examples from the Maidan and Shakar-Dara rivers in Kabul region of the Kabul river basin. As dominant hydrological characteristics of intermittent rivers, the interaction between surface water and groundwater is studied by correlating the precipitation, evapotranspiration, river discharges and groundwater level fluctuations in wells located in the vicinity of the rivers. Suspended sediment transport and river bed sediments are in a further step studied to understand the sedimentological behaviour of these river systems. The characteristics of the catchment area such as geology, land cover, land use and dry periods are studied to show their influence on the suspended sediment transport. Field observations and satellite images are used to investigate the morphology of the selected rivers. Results show that precipitation, in particular during the winter and early spring months exceed the evapotranspiration and are providing the main water source for irrigation and groundwater recharge. The analysis reveals that the seepage loss through the river bed contributes significantly more to the groundwater recharge than precipitation. An increase in suspended sediment concentrations in Maidan river are observed by comparing historic (1965–1968) and recent (2012–2015) data. In addition, higher suspended sediment concentrations are observed in Maidan river compared to Shakar-Dara river. The higher concentrations can be linked to the lower percentage of vegetated area in its catchment compared to the Shakar-Dara catchment as well as to its finer sediment grain sizes of its bed and banks. Morphological investigations indicate single and multi-thread (braided) channels are the most common planform types for Shakar-Dara river, however, at Maidan river with gentle slopes, a meandering tendency with various sinuosities can be observed.

Estimated seepage rates from selected ditches, ponds, and lakes at the Camas National Wildlife Refuge, eastern Idaho

The Camas National Wildlife Refuge (Refuge) in eastern Idaho, established in 1937, contains wetlands, ponds, and wet meadows that are essential resting and feeding habitat for migratory birds and nesting habitat for waterfowl. Initially, natural sources of water supported these habitats. However, during the past few decades, changes in climate and surrounding land use have altered and reduced natural groundwater and surface-water inflows, resulting in a 5-meter decline in the water table and an earlier, and more frequent, occurrence of no flow in Camas Creek at the Refuge. Due to these changes in water availability, water management that includes extensive groundwater pumping is now necessary to maintain the wetlands, ponds, and wet meadows.These water management activities have proven to be inefficient and expensive, and the Refuge is seeking alternative water-management options that are more efficient and less expensive. More efficient water management at the Refuge may be possible through knowledge of the seepage rates from ditches, ponds, and lakes at the Refuge. With this knowledge, water-management efficiency may be improved by natural means through selective use of water bodies with the smallest seepage rates or through engineering efforts to minimize seepage losses from water bodies with the largest seepage rates.The U.S. Geological Survey performed field studies in 2015 and 2016 to estimate seepage rates for selected ditches, ponds, and lakes at the Refuge. Estimated seepage rates from ponds and lakes ranged over an order of magnitude, from 3.4 ± 0.2 to 103.0 ± 0.5 mm/d, with larger seepage rates calculated for Big Pond and Redhead Pond, intermediate seepage rates calculated for Two-way Pond, and smaller seepages rates calculated for the south arm of Sandhole Lake. Estimated seepage losses from two reaches of Main Diversion Ditch were 21 ± 2 and 17 ± 2 percent/km. These losses represent seepage rates of about 890 and 860 mm/d, which are one- to two-orders-of-magnitude larger than seepage rates from the ponds and lake.The depth-integrated vertical hydraulic conductivity (Kv) for sediment underlying the ponds and lake was the primary control of seepage rates. The Kv's were 30 and 34 m/d for Big Pond, 14 and 18 m/d for Toomey Pond, 8 and 10 m/d for Two-way Pond, and 47 m/d for the north arm of Sandhole Lake.

Tracer an effective tool in detecting canal seepage: case studies from Northern India

Canal irrigation is well developed in several provinces of India since independence. With the increase in demand and irregular rainfall, several areas are covered using canal network to suffice agricultural and drinking water needs. Besides its utility and functioning, several problems are associated with canal irrigation, such as seepage losses and water logging. Apart from geophysical and geological methods, tracer is a tool which can be used to study canal seepage. It facilitates in identifying maximum seepage zones and expected seepage path qualitatively and quantitatively without interrupting normal activity of the canal. In this paper, identification of canal seepage in detail with two case studies namely Indira Gandhi Main Canal (IGMC), Rajasthan, and canals in Kakrapar network, Gujarat, from Indian subcontinent is reported. Tracer studies revealed the vulnerable zone, i.e., fractures or cracks in the canal lining with excessive seepage in both the cases. Tracer technique is a definite, reliable and cost effective tool, which provides unique insight into canal seepage investigation.

Optimizing Irrigation Rates for Cotton Production in an Extremely Arid Area Using RZWQM2-Simulated Water Stress

Abstract. Quantifying crop water demand and optimizing irrigation management practices are essential to water resource management in arid desert oases. Agricultural systems modeling can serve to develop a better understanding of the hydrologic cycle under various irrigation and climate conditions. RZWQM2-simulated water stress can be used as an indicator for irrigation scheduling but has not been applied to extremely arid zones. The objectives of this study were to (1) evaluate the performance of RZWQM2 in simulating soil moisture content and crop production in an extremely arid area and (2) develop an optimal irrigation strategy using model-simulated crop water stress. In this study, RZWQM2 hybridized with DSSAT was calibrated and validated against soil moisture, cottield, and development stage data collected from 2006 to 2013 in a flood-irrigated cotton field located in an extremely dry oasis in Cele, situated in Xinjiang, China (mean annual precipitation 37 mm). The simulated water balance was analyzed to determine the actual crop water consumption, crop water requirements, and seepage loss. Subsequently, an optimal irrigation scheme was developed using RZWQM2 by averting crop water stress from planting to 90% open boll. In comparison to similar studies, the accuracy of soil moisture content simulations was deemed acceptable based on percent bias (PBIAS &amp;lt; ±15%), coefficient of determination (0.378 = R2 = 0.636), Nash-Sutcliffe model efficiency (0.130 = ME = 0.557), and root mean squared error (0.022 m3 m-3 = RMSE = 0.031 m3 m-3). The model performed well in simulating cotton yield (R2 = 0.79, ME = 0.75, RMSE = 417.0 kg ha-1, and relative RMSE (rRMSE) = 12.5%). Model-simulated plant emergence dates were generally six days late because of the model’s lack of a component for mulching after seeding. Other phenological dates were closely matched, with a mean difference of ±4 days. On average, over eight years, the simulated growing season (planting to 90% open boll) water balance showed that the cotton crop consumed 532 mm year-1 of water under current irrigation practices, while 109 mm of water was lost through deep seepage. However, based on simulated PET, the crop water requirement was 641 mm year-1, suggesting water stress under current irrigation practices. Under these conditions, water stress occurred mainly during the late stages of cotton growth. The model-simulated actual evapotranspiration (ET) is comparable to the calculated ET using the water balance method, with percent error of -1.3%, indicating the rationality of applying model-simulated results in a water stress-based irrigation scheduling method. On average, the water stress-minimizing RZWQM2 irrigation schedule resulted in an apparent irrigation water savings of 32 mm year-1 (4.9%) and an annual yield increase of 527 kg ha-1 (16.3%). RZWQM2 was shown to be suitable for simulating soil hydrology and crop development in an agricultural system implemented in an extremely dry climate. Rescheduling of irrigation using a water stress-based method can be used to optimize irrigation water use and cotton production. Keywords: Cotton production, Optimum irrigation, RZWQM2, Soil water content, Water stress, WS-based regime.

Estimating Water Balance of Small Reservoirs in Arid Regions: A Case Study from Kachchh, India

Quantification of hydrological processes is necessary for management of small reservoirs especially in arid regions characterized by hot climate, scanty rainfall magnitudes and large rainfall variability. This study focuses on estimating inflow and outflow components of a small reservoir situated in arid Kachchh region of Gujarat, India, by developing a water balance model. Daily reservoir water levels were monitored for years 2012 and 2013. All water balance components, i.e. rainwater directly falling into reservoir, surface runoff, irrigation extractions, and evaporation and percolation, were either measured or estimated. Results indicated that rainfall has a fair control on amount of harvested runoff water. In year 2012, meagre rainfall (79 mm) could store 925 m3 of water with 66 cm depth. In contrast, reservoir water levels were at 2.85 m depth in year 2013 with full capacity of 24,879 m3 when rainfall totalled to 291 mm. The mean percolation rate (0.14 cm h−1), determined from 24-h long-term infiltration tests, revealed that full storage will get depleted within 85 days. A major portion (51%) of storage was lost through evaporation and percolation, and only 21% stored water could be utilized for supplemental irrigation. This finding suggested that suitable measures need to be adopted to check evaporation and seepage losses from the reservoirs in arid regions for improved agricultural productivity. Moreover, results of this study may be useful for water resources managers and decision-makers to develop appropriate operational strategies for the reservoirs in the study area as well as in other arid regions of the world.

Density-dependent water use in carp polyculture: Impacts on production performance and water productivity

The total water use (TWU) and consumptive water use index (CWUI) in carp polyculture under varying intensity levels [T1: 6000fingerlingsha−1, T2: 8000fingerlingsha−1, T3: 10,000fingerlingsha−1] were quantified. Treatment-wise estimated TWU was 3.71×104, 3.92×104 and 4.34×104m3ha−1180d−1 while, the CWUI was 6.38, 5.61 and 5.89m3kg−1 fish production in T1, T2 and T3, respectively. The estimated evaporation and seepage loss ranged between 2.1–3.1 and 1.9–2.8m3waterkg−1 fish production respectively and contributed significantly to consumptive water use (CWU). Treatment-wise sediment load ranged between 57.1 and 61.1m3t−1 fish biomass. Faster growth rate and biomass contribution (%) to yield was maximum by C. catla followed by C. mrigala and L. rohita in all the treatments. In this study, under best management practice (T2), 1m3 of water produced 178g of carp biomass and its economic value per unit of water used (USDm−3) greatly exceeds that of T1 and T3. Among the treatments, minimization of total water use (3.92×104m3), CWU (2.03×104m3) and water exchange (0.20×104m3) at stocking density of 8000fingerlingsha−1 (T2), resulted in higher (P<0.05) yield (3.62tha−1180d−1), output value - cost of cultivation ratio (1.88), net consumptive water productivity (USD 0.15m−3) and lower AFCR (1.74). Further, farming systems with low water exchange, serves to keep the water quality suitable for the fish growth, improves water use efficiency and helps in minimizing the quantity of pollutant outputs. Statement of relevanceThis paper presents findings and analysis, from a methodologically rigorous investigation and provides insight regarding density-dependent optimum water use, its effect on pond water quality, sedimentation rate, growth performance and water productivity. The knowledge derived from this study may be a basis to optimize pond rearing efforts in carp polyculture and the water management strategies can be tailored to prevent wasteful use of water and enhance water use efficiency and water productivity.

Fluxes and production efficiency of irrigated wheat ecosystem under edaphic constraints of western Maharashtra plateau: a micrometeorological investigation

Energy fluxes and canopy microclimate of wheat grown on the edaphically stressed shallow basaltic soil at Baramati, India were studied during 2014-15.The crop was grown with optimum irrigation, applied at frequent intervals, resulting in a low seasonal Bowen ratio (H/LE: Sensible heat flux/Latent heat flux) value of 0.23. The diurnal average flux rate for H during various phenophases varied between 2.2 and 16.2 Wm-2 and had a seasonal mean of 11.0 Wm-2. LE exchange rates varied between 44.2 and 56.8 Wm-2 and the seasonal mean was 49.0 Wm-2.Evapo-transpiration (ET) of wheat in the location under standard growing condition was estimated at 312 mm.However, the crop could actually evapotranspire water in the range of 187-248 mm,as measured through an eddy covariance based protocol, even though it received about 410 mm of water through irrigation and rainfall. Canopy condition were interpreted through hyperspectra based indices, viz. NDVI and LSWI which indicated atleast two instances of stress, one around maximum tillering and the other between anthesis and dough stages.Net primary production and yield during the 105 day long growing season were 558 g C m-2 and 3.3 t ha-1, respectively and the productivity gap could be minimized by addressing the major edaphic limitations, i.e. low soil volume and high seepage losses.