Analysis of Residential Irrigation Distribution Uniformity

Irrigation has become commonplace for residential homeowners desiring high quality landscapes in Florida. The goal of this project was to document irrigation system uniformity in Central Florida and to quantify distribution uniformity of residential sprinkler equipment under controlled conditions. The catch-can testing procedure used was a modified version of both the American Society of Agricultural Engineers standard and Florida Mobile Irrigation Laboratory (MIL) procedures. The modified version included a larger sample size to ensure complete sample collection over the entire irrigated area. The standard MIL procedure may overestimate the uniformity for residential systems. From the tests on residential irrigation systems, the average low quarter distribution uniformity (DUlq) value was calculated as 0.45. Rotary sprinklers resulted in significantly higher DUlq compared to fixed pattern spray heads with 0.49 compared to 0.41, respectively. From uniformity tests performed on rotor and spray heads under ideal conditions, rotor heads had more uniform distributions than the spray heads of 0.55 compared to 0.49, respectively. Spray heads had better uniformity when fixed quarter circle nozzles were used as opposed to adjustable nozzles. Both residential irrigation system and controlled tests resulted in (DUlq) at the low end of industry guidelines. Residential irrigation system uniformity can be improved by minimizing the occurrence of low pressure in the irrigation system and by ensuring proper spacing is used in design and installation.     

Residential Water Savings Associated with Satellite-Based ET Irrigation Controllers

A mixed landscape irrigation study was conducted on 27 residential sites in Las Vegas to quantify water savings associated with satellite irrigation controllers. Seventeen sites were equipped with evapotranspiration-based (ET) satellite irrigation controllers and ten sites were designated as control sites and retrofitted with nonET-based irrigation controllers. Results showed that 13 of 16 ET-based controller sites saved water compared to four of ten of the nonET-based control sites. When all control sites were grouped together, a statistical difference occurred between the control and ET-based groups (ET-based controller=+20% savings) (p<0.05). Results from this study indicated that water savings were not because of deficit irrigations at the expense of the landscape plant material. Eighty-one percent of the variation in the total outdoor water use could be described by the total turfgrass area at each site. Such results would suggest that turfgrass limitations have merit, if the grass being restricted is tall fescue growing in an arid environment.     

Evaluation of Water and Energy Use in Pressurized Irrigation Networks in Southern Spain

A procedure for evaluating water and energy use in pressurized irrigation networks was developed. Performance indicators were derived from the International Program for Technology and Research in Irrigation and Drainage (IPTRID) and the Institute for Diversification and Energy Savings (IDAE) in Spain and applied to ten representative irrigation districts with on-demand pressurized networks during the 2006–2007 irrigation season. The results confirm the high energy requirements needed for operating these irrigation schemes. To apply an average depth of 2,589??m3/ha, the energy required was estimated to be 1,000??kW???h/ha. Power requirements per unit of irrigated area were 1.56??kW/ha and the pumping energy (PE) efficiency was 58%.     

Expanding Disk Rain Sensor Performance and Potential Irrigation Water Savings

Rain sensors (RSs) appear to be a useful tool for water conservation at a relatively low cost. However, little evidence related to RS performance and/or reliability exists. The objectives of this experiment were to: (1) evaluate two RS types with respect to the following: Accuracy of their set point, number of irrigation cycles bypassed, and duration in bypass mode; (2) quantify the amount of water that RSs could save; and (3) estimate their payback period. Mini-click (MC) and wireless rain-click (WL) rain sensor models were monitored. For the WL treatment, the dry-out ventilation windows were set half open, and for the MC treatments, rainfall set points of 3, 13, and 25?mm were established. On average, all treatments responded close to their set points with the WL, 3?mm MC, 13?mm MC, and 25?mm MC treatments averaging 1.4, 3.4, 10.0, and 24.5?mm, respectively. However, some replicates showed variable behavior. The number of times that these sensors shut off irrigation (81, 43, 30, and 8 times, respectively) was inversely proportional to the magnitude of their set point, with potential water savings following a similar trend. Where water costs exceed $0.53 per cubic meter ($2.00 per thousand gallons), the payback period is less than a year for WL and MCs set at 13?mm or less.     

Productivity and Equity of Different Irrigation Schedules under Limited Water Supply

Some irrigation schemes with limited water supply in Central and Southern India follow the area proportionate water distribution based on assumed uniform characteristics of the command area (planned schedule). However in most cases, this planned schedule is overridden by the practice in which users at head draw more than their share of water (actual schedule) due to human factors and technical limitations of the planned schedule. This practice is highly inequitable as users at tail end do not get any water. This paper considers alternative schedules based on full irrigation or deficit irrigation within the framework of area proportionate water distribution in such irrigation schemes and presents the simulation–optimization technique to develop the corresponding land area and water allocation plan for different allocation units by considering the heterogeneity of the irrigation scheme. This paper further demonstrates the utility of proposed alternative schedules by comparing the productivity and equity of these schedules with planned and actual schedules for one irrigation scheme in Central India. The results show that the actual schedule reduces both productivity and equity greatly and the productivity and equity with the alternative schedules are higher than with the planned schedule. The results also show that deficit irrigation has great potential to increase both productivity and equity of irrigation schemes.     

Forecasting Domestic Water Use in Rapidly Urbanizing Areas in Asia

This paper summarizes some of the recent trends in domestic water use in both developed and developing countries, so as to better identify the principal factors influencing the demand. The focus is on the adoption of a more microapproach to demand forecasting, rather than the traditional use of overall averages, so as to move towards more cost effective and resource efficient supply schemes. An important aim of the paper is to alert designers of new water supply schemes in developing countries to the need to apply caution to the belief that per capita water use will continue to increase in tandem with the general economic development of the area being served, to the extent that it reaches the levels experienced in more developed countries. Survey data are presented from a range of locations to illustrate the trends in domestic water use for both connected households and community standpipes.     

Development and Evaluation of Soil Moisture-Based Seepage Irrigation Management for Water Use and Quality

A 2-year study was conducted at a seepage-irrigated vegetable farm in south Florida to develop and evaluate an improved, soil moisture-based irrigation management practice that could potentially reduce irrigation water use, prevent water quality impairment, and maintain or improve crop yield. The improved practice reduced irrigation water use by 36% compared to the conventional irrigation management. Moreover, the improved practice also increased rainfall retention and decreased runoff events by lowering the water table 13?cm compared to the conventional practice. Total dissolved phosphorus (P) concentrations in groundwater were higher (p<0.01) for the improved practice compared with the conventional practice in two of the three fields where ground water quality was monitored. Higher P concentrations for the improved practice were likely due to the dilution effect. Statistically, no differences (p>0.05) were observed in groundwater nitrogen (N) (NOx–N, NH4–N, and total dissolved N) concentrations between the improved and the conventional practices. Similarly, no statistical difference was observed in crop yield between the improved and the conventional practices, although the average total yield was higher for the improved practice. The improved practice also reduced the incidence of plant disease compared to the conventional practice which resulted in crop failure in some fields. Thus, use of the improved practice reduced irrigation water use without impacting crop yield.     

Optimal Irrigation Planning under Water Scarcity

In this study optimal irrigation planning strategies are developed for the Nagarjuna Sagar Right Canal command in the semiarid region of South India. The specific objective of the study is to allocate the available land and water resources in a multicrop and multiseason environment and to obtain irrigation weeks requiring irrigation of a fixed depth of 40 mm. The problem is solved in four stages. First, weekly crop water requirements are calculated from the evapotranspiration model by the Penman-Monteith method. Second, seasonal crop water production functions are developed using the single-crop intraseasonal allocation model for each crop in all seasons. Third, allocations of area and water are made at seasonal and interseasonal levels by deterministic dynamic programming, maximizing the net annual benefit from the project. And fourth, once optimal seasonal allocations have been attained, irrigation scheduling is performed by running a single-crop intraseasonal allocation model. Optimal cropping pattern and irrigation water allocations are then made with full and deficit irrigation strategies for various levels of probability of exceedance of the expected annual water available. The results reveal that the optimization approach can significantly improve the annual net benefit with a deficit irrigation strategy under water scarcity.     

Evaluation of a System for Residential Treatment and Reuse of Wastewater

Approximately one-quarter of housing units in the United States are not connected to centralized, publicly owned wastewater treatment works and instead operate their own cesspools or septic tanks that provide only partial treatment. A study was conducted in which a commercially available, on-site, residential wastewater package unit was tested at its design capacity according to an established protocol to determine if it could produce a high-quality effluent. Additional pilot-scale sand filtration and ultraviolet disinfection units were fabricated and operated to determine the feasibility of producing recycled water suitable for residential reuse and which could meet strict water reuse regulations. The results indicate that the package unit can produce an effluent equivalent to secondary effluent when properly operated and maintained. In addition, using add-on sand filter and ultraviolet light disinfection units, it was possible to produce the highest quality of reclaimed water recognized by Hawaii regulations (oxidized, filtered, disinfected, unrestricted use). It was also possible and may be economically feasible to produce a slightly lower quality reclaimed water (oxidized, disinfected, R-2) suitable for residential subsurface irrigation.     

Irrigation Scheduling. II: Heuristics Approach

A sequential irrigation schedule that honors user demands of duration and minimizes earliness and tardiness is interpreted as a single-machine schedule with earliness and tardiness costs and a common deadline (or fixed interval). A heuristic solution is presented for this irrigation scheduling problem. Four models are presented to reflect the different methods in which an irrigation system at the tertiary unit level may be operated, the first model permits jobs to be noncontiguous, i.e., idle time between jobs is permitted, whereas the others permit contiguous jobs only. The heuristic is tested extensively and the solution quality is compared with either an optimum solution from an integer program or the best available solution obtained from an integer program within allocated computation time. The heuristic is computationally efficient for all models presented, however for schedules with noncontiguous jobs, or where idle time is inserted before and after a contiguous set of jobs, solution quality deteriorates. The work brings the science of single scheduling from operations research into irrigation scheduling and suggests areas for further development.     

Demand Forecasting for Irrigation Water Distribution Systems

One of the main problems in the management of large water supply and distribution systems is the forecasting of daily demand in order to schedule pumping effort and minimize costs. This paper examines methodologies for consumer demand modeling and prediction in a real-time environment for an on-demand irrigation water distribution system. Approaches based on linear multiple regression, univariate time series models (exponential smoothing and ARIMA models), and computational neural networks (CNNs) are developed to predict the total daily volume demand. A set of templates is then applied to the daily demand to produce the diurnal demand profile. The models are established using actual data from an irrigation water distribution system in southern Spain. The input variables used in various CNN and multiple regression models are (1) water demands from previous days; (2) climatic data from previous days (maximum temperature, minimum temperature, average temperature, precipitation, relative humidity, wind speed, and sunshine duration); (3) crop data (surfaces and crop coefficients); and (4) water demands and climatic and crop data. In CNN models, the training method used is a standard back-propagation variation known as extended-delta-bar-delta. Different neural architectures are compared whose learning is carried out by controlling several threshold determination coefficients. The nonlinear CNN model approach is shown to provide a better prediction of daily water demand than linear multiple regression and univariate time series analysis. The best results were obtained when water demand and maximum temperature variables from the two previous days were used as input data.     

Allocation of Scarce Water Resources Using Deficit Irrigation in Rotational Systems

On irrigation schemes with rotational irrigation systems in semiarid tropics, the existing rules for water allocation are based on applying a fixed depth of water with every irrigation irrespective of the crops, their growth stages, and soils on which these crops are grown. However, when water resources are scarce, it is necessary to allocate water optimally to different crops grown in the irrigation scheme taking account of different soils in the command area. Allocating water optimally may lead to applying less water to crops than is needed to obtain the maximum yield. In this paper, a three stage approach is proposed for allocating water from a reservoir optimally based on a deficit irrigation approach, using a simulation-optimization model. The allocation results with a deficit irrigation approach are compared for a single crop (wheat) in an irrigation scheme in India, first with full irrigation (irrigation to fill the root zone to field capacity) and second with the existing rule. The full irrigation with a small irrigation interval was equivalent to adequate irrigation (no stress to the crop). It is found that practicing deficit irrigation enables the irrigated area and the total crop production in the irrigation scheme used for the case study to be increased by about 30–45% and 20–40%, respectively, over the existing rule and by 50 and 45%, respectively, over the adequate irrigation. Allocation of resources also varied with soil types.     

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.     

Monthly Water Resources and Irrigation Planning: Case Study of Conjunctive Use of Surface and Groundwater Resources

The Tehran metropolitan area is one of the mega cities of the world and has an annual domestic water consumption close to one billion cubic meters. The sewer system mainly consists of traditional absorption wells. Therefore, the return flow from the domestic consumption has been one of the main sources of groundwater recharge. Some part of this sewage is drained into local rivers and drainage channels and partially contaminates the surface runoff and local flows. These polluted surface waters are used in conjunction with groundwater for irrigation purposes in the southern part of the Tehran. In this paper, a systematic approach to surface and groundwater resources modeling in the study area, with its complex system of water supply, groundwater recharge, and discharge, is discussed. A dynamic programming optimization model is developed for conjunctive use planning. The objective function of this model is developed to supply the agricultural water demands, to reduce pumping costs, and to control groundwater table fluctuations. To develop the response function of the aquifers located in the study area, a mathematical model for simulation of the Tehran aquifer water table fluctuations has been developed and calibrated with the available data. Different scenarios are defined to study the long-term impacts of the development projects on conjunctive use policies and water table fluctuations. Comparison of the results showed how significant is the effects of an integrated approach to the surface and groundwater resources allocation in Tehran metropolitan area. The proposed model is a useful tool for irrigation planning in this region.     

Regional Salinity Modeling for Conjunctive Water Use Planning in Kheri Command

A one-dimensional water and solute transport UNSATCHEM model is calibrated and validated with a saline water use experiment for wheat and cotton crops. The model is further employed for regional scale salinity modeling with distributed data on soil, irrigation water supply, and its quality from six representative locations from the Kheri command of the Bhakra irrigation system. The wheat–cotton crop rotation, the main rotation in the command, is considered during long-term simulations. The CROPWAT model is used to determine the evapotranspiration requirements of different wheat and cotton crops, while soil water retention parameters are estimated by the RETC model. Atmospheric water and solute boundary conditions are assumed at the top boundary, while free drainage is considered for the lower boundary, as the watertable in the command is sufficiently deep. Simulated salinity and yield values are compared with observed values for regional validation of the model. Critical areas in the command are identified using regional scale modeling results, and applying irrigation water availability and root zone salinity criteria. Guidelines for sustainable conjunctive water use planning are for the Kheri command to get optimum agricultural production despite the use of saline water for irrigation under prevailing scenarios of water availability and its quality.     

Hypochlorite Solution Expiration and Stability in Household Water Treatment in Developing Countries

Household water treatment with dilute hypochlorite solution has been shown to improve microbiological water quality and reduce diarrheal disease in developing countries. One concern raised by governmental agencies, implementers, and nongovernmental organizations is whether the hypochlorite solution remains stable during distribution and after the bottle is opened and usage begins. In this study, laboratory and field research was conducted to determine the expiration date and stability in the home of hypochlorite solution. Expiration-date testing found that pH-stabilized ～ 1.25% hypochlorite solution made using various production techniques in Ethiopia, Guinea, and Nigeria was stable for a minimum of 12 months in temperatures less than 35°C. Stability testing during laboratory simulated normal usage showed no degradation, and 77–91% of bottles collected from households tested met standards. Hypochlorite solution concentration drops rapidly when pH is not stabilized, when pH levels fall, and when solution is exposed to direct sunlight.     

Surface Renewal Estimation of Pasture Evapotranspiration

Experiments to measure the evapotranspiration of an improved, irrigated pasture were conducted at the University of California, Davis, CA field station and over a commercial irrigated pasture on Twitchell Island in the Sacramento-San Joaquin River Delta using the surface renewal (SR) method. In Davis, the SR method was used to determine well-watered crop evapotranspiration (ETc) over short grass, and the results were compared with the ASCE-EWRI standardized reference evapotranspiration (ET0) for a short canopy to establish that a crop coefficient Kc = 1.00 is appropriate for estimating well-watered pasture ETc. In the Twitchell Island study, surface renewal was used to determine the actual evapotranspiration (ETa) from a commercial pasture. A stress coefficient of Ks = ETa/ET0 ≈ 0.90 was observed during the high ET period (ET0>7?mm?day?1) from about mid-June through mid-July for the Twitchell Island pasture. Otherwise, the pasture was mainly unstressed, so the Ks = 1.0. Thus, assuming no future changes in irrigation management, using ET0 from Twitchell Island, a Kc = 1.00, and Ks = 1.00 will provide good estimates of ETa during low to moderate ET periods and Ks ≈ 0.90 should be used when ET0>7.0?mm?day?1. In general, a thermocouple for SR measurements costs about $100, whereas the price for a sonic anemometer varies between $3,000 and $20,000, so the SR method provides a low-cost method to measure ETa.     

General Irrigation Planning Performance of Water User Associations in the Gediz Basin in Turkey

In this study, an evaluation has been made of the realization level of the planned targets in irrigation planning for all of the 13 water user associations (WUAs) of the Gediz Basin. This evaluation was made according to six performance indicators: level of realization of irrigation ratios, level of realization of crop pattern, dependability, adequacy, efficiency, and equity for the years 1999–2002. Seven associations were successful in irrigation ratio realization, and four were successful in crop pattern. Failure of other WUAs can be reduced by collecting farmers’ declarations and evaluating them with greater care and sensitivity. Water delivery in the general irrigation plan was found to be poor with regard to dependability and equity, and good with regard to the indicators of adequacy (except in the year 2001) and efficiency. In order to improve dependability, the period when water is diverted from the source and the period when water is needed must coincide completely. In order to improve equity, delivery of water to WUAs must be carried out taking account of water requirements predicted in the general irrigation plan. When these two indicators are improved, adequacy and efficiency will improve also.     

Sensor-Based Automation of Irrigation on Bermudagrass, during Wet Weather Conditions

New technologies could improve irrigation efficiency of turfgrass, promoting water conservation and reducing environmental impacts. The objectives of this research were to quantify irrigation water use and to evaluate turf quality differences between (1) time-based scheduling with and without a rain sensor (RS); (2) a time-based schedule compared to a soil moisture sensor (SMS)-based irrigation system; and (3) different commercially available SMS systems. The experimental area consisted of common bermudagrass [Cynodon dactylon (L.) Pers.] plots (3.7?m×3.7?m), located in Gainesville, Fla. The monitoring period took place from July 20 to December 14, 2004, and from March 25 to August 31, 2005. SMS-based treatments consisted of irrigating one, two, or seven days a week, each with four different commercial SMS brands. Time-based treatments with or without RS and a nonirrigated treatment were also implemented. Significant differences in turfgrass quality among treatments were not detected due to the sustained wet weather conditions during the testing periods. The treatment with the rain sensor resulted in 34% less water applied than that without the rain sensor (2-WORS) treatment. Most SMS brands recorded irrigation water savings compared to 2-WORS, ranging from 69 to 92% for three of four SMSs tested, depending on the irrigation frequency. Therefore, SMS systems represent a promising technology because of the water savings that they can achieve during wet weather conditions while maintaining acceptable turfgrass quality.     

Method for Evaluation of Depth of Wetting in Residential Areas

Field sampling was performed at a number of residential structures in the Denver metropolitan area for the purpose of assessing the extent of wetting below residential structures after construction and commencement of landscape irrigation. Total suction measurements using filter paper methods were undertaken on undisturbed samples. A similar data set from sites without previous development or irrigation was used to estimate the suction profile before the imposition of residential construction and landscape irrigation. Comparison of the postdevelopment profile measured at the residential structures to the predevelopment profile estimated using a site-specific procedure was used to assess the depth of wetting at each structure. Cumulative probability curves are presented for the depth of wetting arising from common residential landscape schemes and site drainage for the Denver area. The Denver-area data set was used to develop a method for assessment of depth of wetting. This method can be used to assess depth of wetting from residential development for other regions having different climatic conditions and landscape practices.