Application of Watershed-Based Tank System Model for Rainwater Harvesting and Irrigation in India

The SOFTANK model optimally designs the watershed-based tank system by simulating field, tank, and groundwater balances. We applied this model to a small watershed consisting of six tanks (small reservoirs) in the semiarid region of India. We evaluated the existing tank system in this watershed and compared it to a one-tank system. Results showed that one tank at the outlet of the watershed would have been more beneficial [with benefit-cost (BC) ratio of 1.80] than the existing six-tank system (with BC ratio of 1.71). Finally, we performed the analysis for obtaining the optimal tank system for the watershed, and we found that the tanks for irrigation purposes are not economical for the small watershed. The groundwater source was enough for irrigation, so any additional investment in the tanks would be uneconomical. The results demonstrate the importance of the watershed-based tank system approach to design.     

Multilevel Approach for Optimizing Land and Water Resources and Irrigation Deliveries for Tertiary Units in Large Irrigation Schemes. II: Application

The resource allocation model, area and water allocation model, incorporates the concept of deficit irrigation through a variable depth irrigation approach, VDI. It uses this to allocate land and water resources optimally to different crops in a heterogeneous irrigation scheme with limited water under rotational water supply. This model was applied to a medium irrigation scheme in India as a case study, to obtain the land and water allocation plans. These optimal allocation plans were compared to those obtained by using the model with the existing approach (full irrigation with a fixed irrigation interval of 21 days in Rabi and 14 days in the summer season). The allocation plans were obtained taking into account the different parameters that were included in the model, such as crops and cropping pattern, soils, irrigation interval, initial reservoir storage volumes, efficiencies, and the outlet and canal capacities. The total net benefits were compared for the two cases of fixed cropping distribution and free cropping distribution and a sensitivity analysis was conducted on other parameters. Summaries of the allocation plans with the VDI approach are presented for the two cases. The total net benefits obtained with the VDI approach introduced in the model were found to be 22% higher than those obtained with the existing approach. The results of this study are thus indicative of the benefits of deficit irrigation and its application within irrigation schemes that have limited water supply.     

Multilevel Approach for Optimizing Land and Water Resources and Irrigation Deliveries for Tertiary Units in Large Irrigation Schemes. I: Method

This paper presents the area and water allocation model (AWAM), which incorporates deficit irrigation for optimizing the use of water for irrigation. This model was developed for surface irrigation schemes in semiarid regions under rotational water supply. It allocates the land area and water optimally to the different crops grown in different types of soils up to the tertiary level or allocation unit. The model has four phases. In the first phase, all the possible irrigation strategies are generated for each crop-soil-region combination. The second phase prepares the irrigation program for each strategy, taking into account the response of the crop to the water deficit. The third phase selects the optimal and efficient irrigation programs. In the fourth phase of the model, irrigation programs are modified by incorporating the conveyance and the distribution efficiencies. These irrigation programs are then used for allocating the land and water resources and preparing the water release schedule for the canal network.     

Analysis and Synthesis of Transmission Loss Hydrographs

Accounting for transmission losses properly is critical in hydrologic analyses in arid and semiarid climates. The objective of this research was to develop a model that could account for the spatial and temporal variations of transmission losses while routing the flow hydrograph through the channel reach. This model was based on Hortonian infiltration methods and hydrologic channel routing. While most transmission loss models predict flow volumes, the model developed herein uses hydrographs of individual storm events. A numerical optimization procedure was used to identify optimum parameter values for each of Horton’s parameters and the routing coefficient, which were then used in modeling transmission losses. Flow gauge data were obtained from the Walnut Gulch Experimental Watershed, which is located near Tucson, Ariz. Testing of this model indicates that it is able to account for transmission losses and predict downstreamflow with reasonable accuracy. To provide a measure of verification, the model was compared to predictions from Lane’s model, which is a commonly used method of accounting for transmission losses based on upstreamflow and downstreamflow volumes. Overall the two methods were found to agree fairly well though differing assumptions in the methods influence the results.     

Uniformity Distribution and its Economic Effect on Irrigation Management in Semiarid Zones

The management of water resources in irrigation is a fundamental aspect for their sustainability. For correct management, several tools and systems for decision making are necessary. Among the large number of factors that affect the optimization of water use, we must focus on irrigation uniformity and its economic implications. The following methodology, implemented in a computer model, allows us to carry out an economic analysis of the effects of different Christiansen’s uniformity coefficients (CU), which are useful for system design and calculation and also for irrigation management in order to obtain maximize gross margin. In the zone studied (Hydrogeologic System 08.29, Castilla-La Mancha, Spain) working with a solid set system and with four crops (barley, garlic, maize, and onion), there is an economic interest in designing systems with a high CU (90%) that allows us to obtain a high application efficiency (Ea). Regarding the economic optimization of the irrigation depths, the results show that the optimum gross depths are always lower than the irrigation depths for maximum crop yield. The higher the CU, the lower the depths, while the crop yield increases and the gross margin of the crop improves. These general results present significant differences among crops, according to their water requirements and their economic profitability.     

Evaluating the Impact of Daily Net Radiation Models on Grass and Alfalfa-Reference Evapotranspiration Using the Penman-Monteith Equation in a Subhumid and Semiarid Climate

Net radiation (Rn) is the main driving force of evapotranspiration (ET) and is a key input variable to the Penman-type combination and energy balance equations. However, Rn is not commonly measured. This paper analyzes the impact of 19 net radiation models that differ in model structure and intricacy on estimated grass and alfalfa-reference ET (ETo and ETr, respectively) and investigates how climate, season and cloud cover influence the impact of the Rn models on ETo and ETr. Datasets from two locations (Clay Center, Nebraska, subhumid; and Davis, California, a Mediterranean-type semiarid climate) were used. Rn values computed from the 19 models were used in the standardized ASCE-EWRI Penman-Monteith equation to estimate ETo and ETr on a daily time step. The influence of seasons on the estimation of Rn and on estimated ETo and ETr was investigated in winter (November–March) and summer (May–September) months. To analyze the influence of clouds on the impact of Rn models, relative shortwave radiation (Rrs) was used as a means to express the cloudiness of the days as: 0 ≤ Rrs ≤ 0.35 for completely cloudy days; 0.35相似文献   

Microbial Populations in Tropical Reservoirs Using Flow Cytometry

Flow cytometry was applied in the study of bacteria and phytoplankton populations in five tropical reservoirs. Water quality between different reservoirs was compared and correlation analyses were carried out to investigate how the biomass of bacteria and phytoplankton related to other water quality parameters measured (i.e., temperature, dissolved oxygen, pH, conductivity, water transparency, turbidity, chlorophyll a, and total nitrogen and phosphorus). Average chlorophyll a concentrations were typically greater than 20?μg/L. Bacteria populations detected with flow cytometry were generally small in size (typically <0.08?μm3 or 0.3?μm equivalent spherical diameter) and contributed less than 13% of the total microbial biomass. Subpopulations of pico-, ultra-, and net phytoplankton were discriminated flow cytometrically by their red and orange autofluorescence. Cyanobacteria dominated four out of the five reservoirs in terms of numbers but only contributed more than 50% of the microbial biomass in two of the reservoirs. In general, local reservoirs were found to be phosphorus limited and alkaline conditions favored the growth of phytoplankton and bacteria.     

Comparison of Simulation and Experimental Data of a Zero Energy Home in an Arid Climate

In this study, a widely used software package, Trace 700 was used to simulate the energy consumption of the heating and cooling loads of two residential homes and compare them with their experimental values. One home is classified as a zero energy home (ZEH) and employs advanced construction features, which is designed to consume significantly less energy than a normal home. The baseline home is of the exact same dimensions and floor plan as the ZEH, but uses more traditional construction practices. Trace was used to model both homes during periods where both cooling and heating were used, respectively, for an available period of two weeks in 2005. Actual weather data from the vicinity were obtained during the monitoring phase and were introduced into Trace as input data to create a more accurate representation of the conditions. The difference between the simulated predictions and the actual experiments showed an average difference of 2.25 and 6.29% for the baseline house for cooling electric energy and heating energy, respectively, while that difference was 10.67% in cooling for the ZEH. No estimate is presented to the difference in the heating mode for the ZEH due to a plumbing problem. The data showed the ZEH reduced the cooling load by about 76% experimentally and 75% by simulation. The simulation comparison between the baseline and ZEH indicate a reduction of the heating load of about 12%.     

Evaluation of Dust Palliatives for Unpaved Roads in Arid Climates

An evaluation of commercial and experimental dust palliatives was conducted to determine their effectiveness for mitigating fugitive dust on roads in arid climates. Several types of chemicals were tested including polymer emulsions, lignosulfonates, chloride salts, synthetic fluids, an asphalt emulsion, a polysaccharide solution, a polyacrylamide, and a guar gum. Each product was placed in an individual test section at a rate of 3.8?L/m2 using an admix construction method (grade/spray/till/compact/spray). Fourteen test sections were constructed and observed at 30-day intervals to monitor product performance. Data from both stationary and mobile particle collectors were analyzed to determine the ability of each product to suppress dust for extended periods. Several products are recommended for use on roads in arid climates as a result of this evaluation.     

Optimization of Watershed Control Strategies for Reservoir Eutrophication Management

A vital key to the development of a reservoir eutrophication management strategy is to link the watershed-nutrient model to the model of reservoir water quality. To develop a cost-effective optimization model, a coupled watershed-reservoir model with an optimization model has been developed to design control strategies in the watershed in a planning time horizon. This methodology can help reduce the phosphorus concentration of a reservoir to the standard level. In this study, the weather data for the next 10 years was generated using downscaled GCM data to simulate the watershed phosphorus load using the SWAT model. Then an optimal model for selection and placement of best management practices (BMP) at watershed scale is developed by linking the coupled watershed and reservoir models with a genetic algorithm. This model is able to identify the minimum present cost design (type and location) of BMP structural alternatives. The objective of water quality is obtained using a system dynamic model for reservoir phosphorus concentration to determine a permissible phosphorus load as the main agent of eutrophication in a reservoir. Structural BMPs in this study include, filter strips, parallel terraces, grade stabilization structures, and detention ponds. The optimum solution was obtained through a trade-off curve between cost and exceedance magnitude from the standard of reservoir phosphorus concentration. The case study is the Aharchai River Watershed upstream of the Satarkhan Reservoir in the northwestern part of Iran.     

Coupled Crop and Solid Set Sprinkler Simulation Model. II: Model Application

In this work, applications of the coupled solid set sprinkler irrigation and crop model AdorSim introduced in the companion paper are presented. The sprinkler irrigation model is based on ballistic theory, while the crop model is based on CropWat. AdorSim was used to evaluate the effect of sprinkler spacing on seasonal irrigation water use (WU) and crop yield. The most relevant results were related to the characterization of advanced irrigation scheduling strategies. The differences in crop yield and WU derived from irrigating at different times of the day were estimated for two locations strongly differing in wind speed. Irrigation guidelines were established in these locations to relate gross water use and water stress induced yield reductions. Simulations were also applied to estimate adequate wind speed thresholds for irrigation operation. In the experimental conditions, thresholds of 2.0–2.5?m?s?1 proved effective to control yield reductions and to minimize WU.     

History and Evaluation of Hargreaves Evapotranspiration Equation

A brief history of development of the 1985 Hargreaves equation and its comparison to evapotranspiration (ET) predicted by the Food and Agricultural Organization of the United Nations (FAO) Penman-Monteith method are described to provide background and information helpful in selecting an appropriate reference ET equation under various data situations. Early efforts in irrigation water requirement computations in California and other arid and semiarid regions required the development of simplified ET equations for use with limited weather data. Several initial efforts were directed towards improving the usefulness of pan evaporation for estimating irrigation water requirements. Similarity with climates of other countries allowed developments in California to be extended overseas. Criticism of empirical methods by H. L. Penman and others encouraged the search for a robust and practical method that was based on readily available climatic data for computing potential evapotranspiration or reference crop evapotranspiration (ETo). One of these efforts ultimately culminated in the 1985 Hargreaves ETo method. The 1985 Hargreaves ETo method requires only measured temperature data, is simple, and appears to be less impacted than Penman-type methods when data are collected from arid or semiarid, nonirrigated sites. For irrigated sites, the Hargreaves 1985 ETo method produces values for periods of five or more days that compare favorably with those of the FAO Penman-Monteith and California Irrigation Management Information Services (CIMIS) Penman methods. The Hargreaves ETo predicted 0.97 of lysimeter measured ETo at Kimberly, Idaho after adjustment of lysimeter data for differences in surface conductance from the FAO Penman-Monteith definition. Monthly ETo by the 1985 Hargreaves equation compares closely with ETo calculated using a simplified, “reduced-set” Penman-Monteith that requires air temperature data only.     

Operative Approach to Agricultural Drought Risk Management

In a companion paper, the agricultural drought economic risk assessment (ADERA) model was described. ADERA studies agricultural drought not only in terms of deficit soil water content and its frequency and severity (as in the traditional approach) but also in terms of net benefit reduction and vulnerability. The relationship between drought index, crop yield, and crop economic net benefit is modeled and three threshold levels are considered: the critical water content; the critical impact in terms of net benefit; and its critical return period (i.e., frequency) above which the soil-climate unit is considered unsuitable for the cultivation of a specific crop. These critical levels are used in long-term action planning as the triggers for different risk classes. The rapidity with which the critical impact is reached is considered indicative of the crop vulnerability, and real-time monitoring of the impact evolution (short-term actions) is also implemented. Initially ADERA was applied at only one point (soil-crop-climate unit), but because agricultural drought is by definition a wide area phenomenon, the model must be validated in other units and then used to evaluate the drought area extension (risk map). In this paper, generalization, demonstration, and guidance on the application of ADERA are given with reference to rainfed sunflower and sorghum crops in six soil-climate units in central Italy for which time series for yield (obtained in experimental plots where the water scarcity was the principal factor limiting the final yield) since 1978 is available. The application of ADERA made it possible to quantify the vulnerability class and the corresponding risk class for the single unit (long-term action planning). The analysis results confirm that typically for the selected crops the critical impact has a low risk and a low vulnerability. In fact sunflower and sorghum are rainfed crops widely cultivated in the area under investigation. Moreover, the results show that each risk class is present only within a specific cost range, in particular the upper and lower limits, and the size of each cost range varies according to the different units; the occurrence of a specific risk class and vulnerability level is highly correlated with the selected triggers, in particular with the critical net benefit (for an increment of which above the corresponding cost range, a given soil-climate unit can become unsuitable for the cultivation of a specific crop); the critical water content is a normal occurrence event for all the units analyzed, with the crop water stress onset date always around 40% of the growing period being a typical characteristic of the specific area, of the two crops and of the selected drought index. The practical usefulness of the impact monitoring procedure was stressed by comparing its progressive evolution in the cases of both a rainfed crop and of a rescue irrigation carried out at a selected and opportune date. In the latter case the impact was reduced below the critical level.     

Interbasin Water Transfer: Economic Water Quality-Based Model

The interbasin water transfer project is an alternative to balance the nonuniform temporal and spatial distribution of water resources and water demands, especially in arid and semi arid regions. A water transfer project can be executed if it is environmentally and economically justified. In this study, the feasibility of two interbasin water transfer projects from Karoon River in the western part of Iran to the central part of the country is investigated. An optimization model with an economic objective function to maximize the net benefit of the interbasin water transfer projects is developed. The planning horizon of the model is 23 years (the length of historical data); and it is solved using genetic algorithm. In order to consider environmental impacts of water transfer projects, a water quality simulation model has been used. Then, an Artificial Neural Network model is trained based on the simulation results of a river water quality model in order to be coupled with the optimization model. The outputs of the optimization model are the value of economic gain of the sending (Karoon) basin to offset the loss of agricultural income and environmental costs. The optimal polices for water transfer during the planning horizon has been generated using the coupled simulation-optimization model. Then, operating rules are developed using a K Nearest Neighborhood model for the real time water transfer operation. The results show the significant value of using the proposed algorithm and economic evaluation for water transfer projects.     

Incorporating Reservoir Transfer into Treatment Optimization Decisions

The Massachusetts Water Resources Authority (MWRA) supplies unfiltered water from two large surface water reservoirs to the metropolitan Boston area, as well as to three smaller communities in central Massachusetts [the Chicopee Valley Aqueduct (CVA) communities]. Quabbin Reservoir is larger than Wachusett Reservoir, and has traditionally been used to supplement the Wachusett during the summer period. Quabbin water is also of better quality, with lower reactive natural organic matter (NOM). The MWRA began to add chlorine at Wachusett in 1997, and a new facility for adding chlorine at Quabbin for the CVA was also started up in 2000 to meet primary disinfection regulations to meet pathogen inactivation. The reaction of chlorine with NOM produces undesirable disinfection by-products (DBPs). The absorption of ultraviolet light at a wavelength of 254 nm was identified in chlorine decay studies to be the most important raw water quality parameter for predicting chlorine decay and DBP formation. This technical note summarizes the chlorine decay model for Wachusett and Quabbin water. The model is extended to ozonation of Wachusett water for the future Walnut Hill treatment plant. The models allowed the development of a trigger using UV-254 to time the Quabbin transfer to optimize treatment results. It is believed that the model for disinfectant decay and the use of UV-254 as a trigger for water treatment decisions are generalized and applicable to other water utilities.     

Estimating Air Vapor Pressure in a Semiarid Region Using FAO-56 Methodology

This paper presents three models for the estimation of vapor pressure from temperature and humidity data as suggested by Food and Agriculture Organization (FAO) Irrigation and Drainage Paper No. 56 (FAO-56) that have been compared for their performance using daily data from 2002 through 2007 for a semiarid climatic region of Udaipur in Rajasthan, India. Vapor pressure data obtained from dew-point temperature has been used as actual vapor pressure. Model?1 performed better than the remaining two models. Lower values of vapor pressure are better modeled by the three models than higher values. The average absolute error of Model?1 varied from 5.09 to 15.59%, of Model?2 from 5.59 to 19.73%, and that of Model?3 from 5.62 to 37.21%. Estimates of vapor pressure obtained from the three models were also used to estimate open-water evaporation determined by the modified Penman method; the results were compared. Errors in vapor pressure data did not significantly affect estimates of evaporation, indicating that other factors such as energy budget played a much more significant role than mass transfer influence for this arid basin. Errors in evaporation estimation were <4% for Model?1, <9% for Model?2, and <14% for Model?3. Even for Models?2 and 3 they were <6% for most months. In general, Model?1 was found to be the best model of vapor pressure estimation and also caused the fewest errors in estimation of evaporation.     

Optimal Sizing of On-Farm Reservoirs for Supplemental Irrigation

A model was developed for prediction of the optimal size of an on-farm reservoir (OFR) so as to provide supplemental irrigation to rice in monsoon season and presowing irrigation to mustard in winter for a rainfed farming system of eastern India. Daily simulations of water balance parameters of both the cropped field and the OFR, economic analysis, and irrigation management practices were inputs to the model. The study predicted an OFR of depth 2 m requiring 12% of the 800 m2 farm area with a volume of 61 m3 to be optimum. The above-mentioned optimal size of the OFR gave a benefit-cost ratio (BCR) of 1.22, internal rate of return (IRR) of 15%, and pay back period (PBP) of 15 years. Simulated results were verified by conducting three years of field experiments to justify the investment in the OFR irrigation system. The observed BCR, IRR, and PBP from the experimental study were 1.17, 14.8%, and 16 years, respectively. There was an increase of 39 and 15% in the yield of rice grain and mustard seed over rainfed conditions because of application of 84 and 45 mm of supplemental irrigation, respectively.     

New Methodology for the Risk Analysis and Economic Impact Assessment of Agricultural Droughts

The paper proposes a new methodology that studies agricultural drought not only in terms of deficit soil water content, its frequency and severity, as in the traditional approach, but also in terms of net benefit. For this purpose the relationship between drought index, crop yield, and crop economic net benefit is modeled and three threshold levels are considered. The first is the critical water content, below which the crop faces water stress (termed as potential agricultural drought). The second is the critical net benefit, below which there is meager (e.g., zero) profit (termed as actual agricultural drought). The third is the critical return period (or frequency) of the actual agricultural drought, below which there is an agricultural aridity (almost steady phenomenon with high impact, high risk) and above which there is an agricultural drought (occasional phenomenon with high impact, low risk). To pinpoint the time of occurrence of the potential and the actual agricultural drought, real-time monitoring is conducted. The rapidity with which these critical conditions are reached is considered as indicative of the crop vulnerability to the corresponding phenomenon. The evolved methodology therefore is based on an objective definition of agricultural drought and is formulated accounting for its peculiar characteristics. The methodology is called the risk analysis and economic impact assessment of agricultural drought (ADERA). ADERA is applied to the rainfed sunflower crop in the Papiano (central Italy) experimental plots for which the 26-year time series for yield and the corresponding phenological, climatic, and economic data are available. The drought index-crop yield-crop economic net benefit relationship makes it possible to quantify the frequency (return period) of the actual agricultural drought and to show that for the given costs and crop sale price the actual agricultural drought risk for the crop is low. For the case study, the vulnerability of the unit to the agricultural drought is low, as the critical net benefit typically occurs late in the growing season.     

Resolving Disputes over Reservoir-River Operation

The main objective of this work is to allocate water with acceptable quality from a reservoir-river system to different water users and to determine the maximum acceptable pollution load that each user discharges to the river. To achieve this, a bargaining model is developed based on a system dynamics approach, and it is compared with an alternative model based on the Nash bargaining theory. The quality of water released from the reservoir is assessed considering selective withdrawal schemes, obtained from schemes based on operating rules derived from an artificial neural network (ANN) and a K-nearest neighborhood (NN) model. A river water-quality simulation model is also linked with the two bargaining models. These models are then applied to the Karkheh reservoir-river system and using a 50-year monthly time series of qualitative and quantitative data of this system. Finally, the performance criteria for the results of the models are determined and compared. This study shows the significant value of the system dynamics approach in resolving disputes over water allocation among stakeholders/water users of reservoir-river systems considering the water-quality aspects.     

Prediction of Water Vapor Movement through Waste Rock

Evaporative losses from the surface of barren waste rock piles in arid environments occur as a result of water vapor diffusion. Water vapor diffusion is accompanied by adsorption of water vapor. A review of the literature found that adsorption of water vapor is commonly described as a sigmoidal function of suction with a predominant linear portion when plotted against the log of suction. Laboratory column tests were conducted with glass beads and waste rock to study water vapor diffusion. A monitoring system was developed for measuring relative humidity and temperature through the column. Water vapor fluxes and relative humidity profiles through the column were measured under steady-state conditions to establish the method of estimating the water vapor diffusion coefficient. Transient water vapor fluxes and relative humidity profiles were measured and a numerical model was developed to simulate the laboratory observations. The numerical model demonstrated the importance of water sorption in controlling the transient water vapor flux. Sorption described as a log–linear function of suction gave reasonable results for the numerical modeling of the glass beads and waste rock.