CASE STUDIES OF AGRICULTURAL WATER CONSERVATION1

Farmers from four irrigation districts in Texas and California were questioned about water conservation practices they are now using, those they plan to adopt, and potential incentives that government might offer to induce still further water conservation on their part. While responses differed somewhat from place to place and among individual farmers, the general results were: a) farmers reported that “water conservation” is not new to them, it is something they practice regularly; b) recent innovations such as laser controlled land leveling devices have permitted some substantial water use reductions in recent years; and c) even greater incentive mechanisms that government could provide and that farmers would accept as useful incentives, such as long term low interest loans for water saving equipment, would probably not be able to reduce water use in agriculture much further than 15 percent below current levels. It is recommended nonetheless that Federal agencies and local water districts and individuals should nonetheless pursue water conservation training and education programs, demonstrations of conjunctive use and water banking opportunities for water saving, and increased loan programs for installation of water saving equipment.     

SOCIAL OVERHEAD CAPITAL COSTS OF IRRIGATION DEVELOPMENT IN WASHINGTON STATE1

ABSTRACT: Increased irrigation as a means of achieving economic development can impose significant social costs on the state or region of growth. The growth in population induced by additional irrigation will require new roads, water and sewage facilities, schools, fire and police protection, etc. Also the increased energy demands due to irrigation and growth in economic activity must be met. Capital investments required to service these needs of new development can become very large. This study attempts to measure such social overhead costs or irrigation development for some specific irrigation project areas of Eastern Washington. It is shown that investment costs in overhead items can reach $2,000 per acre irrigated or $70,000 per job created. Alternatively, the annual costs can equal $180 per acre or $6,700 per worker. These costs must be paid locally through increased taxes, utility rates, or costs for services.     

IMPROVING IRRIGATION RETURN FLOW QUALITY WITH A WATER RENTAL MARKET1

ABSTRACT: Current policies for correcting the problem of irrigation return flow pollution tend to attack the symptoms of the problem, rather than its cause. The present institutional arrangement for allocating irrigation water is seen as the source of the problem. This paper examines the water quality benefits of altering the institutional arrangement to allow for irrigation water transfers through a rental market. It is conceptualized that by creating a water rental market an opportunity cost would be associated with the use of irrigation water such that profit maximizing farmers would be induced to use his water supply more efficiently and rent the surplus to other irrigators, thus reducing return flow pollution. It is shown that a water rental market could increase water quality in the Yakima River in southcentral Washington by 31 percent as well as increase farm incomes and crop production.     

DEVELOPING COMPETITION FOR WATER IN THE URBANIZING AREAS OF COLORADO1

ABSTRACT: Rapid population growth in the metropolitan area of Denver, Colorado, is causing conflicts over water use. Two cities, Thomton and Westminster, have begun condemnation proceedings against three irrigation companies to secure agricultural water rights for municipal use. This is the first condemnation proceeding against irrigation water rights for municipal use. Should the suit succeed, over 30,000 acres of presently irrigated land will lose its water supply. There are about four hundred landowners in the area; two hundred of these are commercial farmers, including truck, dairy and specialty farms. Total agricultural production amounts to about $8 million per year. About 561 jobs related to agriculture will disappear along with about $4 million in not income. Only 6.4 percent of the farmland along the Front Range is irrigated. Continued urban growth will put pressure on the water supply of much of this land. The interested parties of the region should cooperate to lessen the impact of urban growth on agricultural lands and water by forming a metropolitan water district. Such a district could share costs of development of additional municipal water and develop systems where municipalities would recycle waste water back to the irrigated lands.     

Understanding farmer intentions to connect to a modernised delivery system in an Australian irrigation district: a reasoned action approach

Australian governments have sought to invest in irrigation infrastructure to improve the efficiency of water delivery to rural properties and improve water supply and on-farm efficiency. A programme of rationalising irrigation infrastructure has attracted criticism and doubts about its likely success. Attitude theory in the form of the Reasoned Action Model was applied to understand the intentions of landowners to connect to a ‘modernised’ irrigation system. Attitudes towards connecting to the system, social norms and perceptions of control over the behaviour provided an explanation of intentions to connect. Actual financial capability and other variables were important in discriminating a group of landowners who had already connected to the modernised system from farmers who had not.     

Variable Irrigation District Action in Water Trading

Irrigation districts (IDs) in the American west are highly diverse in their economic attributes and local water scarcity circumstances. This diversity may affect reallocative action via water transactions as scarcity rises. The institutional background defining and constraining IDs is described here. For a Texas study region the progress of permanent water right transfers involving IDs is documented and examined. An econometric analysis of multiple decades of ID water transfer activities in the Lower Rio Grande Valley finds that IDs with larger initial water right holdings and higher populations in nearby cities are more likely to participate in agricultural‐to‐municipal water transfer activities. The findings suggest that consolidation of smaller water right holding IDs may be an avenue for quickening the pace of reallocation, especially in more populated areas.     

节水灌溉与控释肥施用对太湖地区稻田土壤氮素渗漏流失的影响

在太湖流域采用田间小区试验研究了干湿交替节水灌溉与控释肥(控释BB肥与树脂包膜尿素)施用对稻田30 cm深土壤渗漏水总氮(TN)、铵态氮(NH+4-N)、硝态氮(NO-3-N)和亚硝态氮(NO-2-N)浓度的动态变化及氮素淋失的影响.结果表明:各处理渗漏水TN、NH+4-N和NO-2-N浓度均在施肥后10 d内达到高峰,然后逐渐下降.渗漏水氮素以NH+4-N(0.22~15.15 mg·L-1)为主,平均占TN 70.1%,NO-3-N(0.10~0.95 mg·L-1)占TN比例较低,平均为13.0%,NO-2-N(0~0.24 mg·L-1)平均仅占TN 1.3%.与淹灌相比,节灌对稻田渗漏水氮素浓度及各氮素占总氮的比例影响不大,但降低了14.2%的渗漏水量和9.4%的TN淋失量.施氮显著提高了渗漏水氮素浓度以及NH+4-N和NO-2-N占TN的比例.控释BB肥和树脂包膜尿素较常规尿素处理水稻全生育期渗漏水TN平均浓度分别降低10.2%和43.3%,TN淋失量分别降低26.1%和39.5%.综上,干湿交替节灌结合树脂包膜尿素施用有利于降低氮素渗漏损失,促进农田面源污染减排.     

Sustainable graywater reuse for residential landscape irrigation – a critical review

The demand for potable water is rising rapidly due to an ever-increasing population, economic activities, and dwindling water supplies. To provide adequate water supplies in the future, understanding the issues and challenges in the reuse of water and developing appropriate strategies for reuse will be critical. One way to augment water supplies for residential use is to reuse graywater – the wastewater from kitchens, bathrooms, and laundries. In this article, we critically review the evolution of water reuse, the definition of graywater, graywater reuse practices, volumes and flow in different situations, and graywater characteristics. We then examine the issues associated with different graywater treatment methods and how using graywater for irrigation around homes affects soil quality and plant growth. The study concludes that graywater treatment costs, human health risks, and its effect on soil quality are some of the challenges that need to be addressed in the future for widespread and sustainable reuse of graywater for irrigation around homes.     

节水灌溉和控释肥施用耦合措施对单季稻田CH4和N2O排放的影响

以我国华东地区典型单季稻水稻田(江苏宜兴)的原柱状土为研究对象,通过两年土柱观测试验,研究不同灌溉管理模式(长期淹水CF、间隙灌溉Ⅱ、控制灌溉CI)和氮肥施用(不施氮CK、尿素Urea和控释肥CRF)耦合措施对水稻生长期内CH4和N2O排放和产量的影响,以期优选典型单季稻田减排增效的水肥管理模式.结果表明,两种节水灌溉方式(CI和Ⅱ)均显著影响稻田土壤CH4和N2O排放量及二者的综合温室效应(GWP)和排放强度(GHGI),与CF相比,Ⅱ和CI均显著提高了 N2O排放量(P＜0.05),降低了 CH4排放量(P＜0.05),进而二者的GWP和GHGI分别显著降低28.9％～71.4％和14.3％～70.4％(P＜0.05);两种节水灌溉模式相比,CI较Ⅱ模式呈现较好的CH4减排优势,排放总量降低了 57.7％～91.8％,而二者的N2O排放量无显著性差异(P＞0.05),最终CI对GWP和GHGI的减排效应略优于Ⅱ模式2.0％～56.2％.施用氮肥(Urea和CRF)均显著促进N2O排放18.4％～2547.8％(P＜0.05),其中CRF处理N2O排放量均略高于Urea处理32.7％～78.6％,但无显著性差异(P＞0.05);CH4排放总量对施氮处理的响应随水分管理模式的不同而不同,总体而言,施用CRF较Urea对稻田土壤GWP和GHGI均无显著影响(P＞0.05).相关分析表明,2018年CF模式的Urea处理和Ⅱ模式的Urea、CRF处理中N2O排放通量与田面水NH4+-N浓度分别呈现显著(P＜0.05)和极显著的正相关关系(P＜0.01),而二者在2019年CI模式的CK和CRF处理中呈现相反规律;2018年CI模式下CK、CRF处理的N2O排放通量与田面水NO3--N浓度呈极显著的正相关关系(P＜0.01).节水灌溉和氮肥施用对水稻产量均呈显著影响(P＜0.05),与CF相比,两种节水灌溉模式(Ⅱ、CI)水稻产量均下降了 14.7％～37.7％;CRF处理较Urea处理略提高水稻产量2.5％～7.4％(P＜0.05).综合考虑稻田土壤GWP、GHGI和水稻产量,节水模式与控释肥施用对稻田土壤减排增产的耦合效应仍有待进一步研究.     

Integration of technologies and alternative sources of water and energy to promote the sustainability of urban landscapes

Recent research has highlighted the positive role of green areas in urban environments, providing numerous social, environmental and economic services, such as mitigation of the urban heat island effect, storm attenuation, increased water infiltration into the soil, reduction of noise and air pollution, among others. However, the maintenance of green areas may result in high consumption of water, reaching 50% of the total consumption in some municipalities, and energy, becoming a reason of concern. The present study aimed to integrate techniques and technologies that promote the automatic and efficient irrigation of urban landscapes, using alternative sources of energy and water, toward its sustainability. The conceptual unit was able to reduce in 64% the water consumed in irrigation. Rainwater met 69% of the demand and the photovoltaic system supplied all the energy required. The economic feasibility analysis showed that the conceptual unit is financially unfeasible, under the conditions of this study. However, with some interventions for reusing the surplus energy and water, and considering the higher fees charged by other cities, the investment became attractive. In this new scenario, the internal rate of return (15 years) was 27.3% and the discounted payback period was 4.9 years.