Implementing irrigation: Salt and nitrate exported from the Lerma basin (Spain)

The creation of a new irrigated area influences the pollutants exported from the zone and, consequently, the quality of receiving water bodies. The aim of this study was to analyze the masses of the main pollutants exported by an area before and during its gradual transformation into irrigated land. To this end, salinity balances were carried out and the nitrate exported from the Lerma basin (752 ha, Spain) was quantified during 2004–2008. The agroenvironmental impact was evaluated through the use of pollution indices. The results revealed that the transformation of the area into irrigated land decreased salinity and increased nitrate concentration in drainage. The increase in the volume of drainage increased the masses of salt and nitrate exported, which in turn increased pollution indices during the transition. However, these indices were still lower than those quantified in other irrigated lands and therefore can still be considered to be of low contamination level. This study demonstrates the important environmental influence of introducing irrigation to an area, as pollution levels change and become mainly dependent on the management of irrigation and nitrogenous fertilization. For this reason, it is highly desirable to promote the optimization of agricultural management in a way that minimizes its impact.     

Analysis of uniformity of sprinkle irrigation in a semi-arid area

One of the most appropriate sprinkler systems for arid or semi-arid areas – where a great deal of irrigating water is required – are the permanent set systems and the continuous-move laterals. To know the reality of water application in this type of areas, many field evaluations of solid set systems and centre pivot irrigation were conducted in Castilla-La Mancha region (Spain). The main factors affecting water application and evaporation and drift losses with these systems (pressure, wind speed, sprinkler type, etc.) were analysed. A set of performance guidelines and recommendations for the design and management of sprinkle irrigation is presented to attain the highest uniformity and efficiency in water application in semi-arid areas. To use working pressure as low as possible, but with sprinklers that produce a great deal of middle size water drops along with night irrigation for minimising evaporation and drift losses are important aspects.     

SIRIAS: a simulation model for sprinkler irrigation

Uniformity of distribution in irrigation systems plays an important role in the optimum use of irrigation water, with direct repercussions on water-use efficiency and production. To evaluate the effects of the wind on sprinkler water uniformity, it is necessary to measure infield water distribution under different wind conditions and then calculate the parameters that define water distribution. This paper perfects the SIRIAS simulation model for sprinkler systems, which can be used to design new irrigation installations or to improve existing ones. Using ballistic theory to simulate the trajectory of drops discharged by the sprinkler, the model obtains wind-distorted water distribution, with a new formulation for the air drag coefficient. It takes into account three options to distribute the evaporation and drift losses in the irrigation process. SIRIAS software has been programmed using Delphi language for Windows 95, 98 and NT.     

Agro-environmental evaluation of irrigation land: I. Water use in Bardenas irrigation district (Spain)

Non-point agrarian contamination makes its allocation to a specific territory difficult. This first part of the study seeks to analyze contamination resulting from water use in 54,438 ha of Bardenas irrigation district included in the Arba basin (BID-Arba). To this end, water balances were carried out in BID-Arba by means of measuring or estimating the main inputs, outputs and water storage between 1 April 2004 and 30 September 2006. Also, the spatial-temporal variability in water use was analyzed.The semester error balances were acceptable (between 11% and −6%), which permits the attribution of the mass of pollutants exported in drainage to the irrigation area evaluated, the objective of the second part of the study. Irrigation efficiency (IE) in BID-Arba was high (90%) despite the fact that Irrigation Sub-District VII (ISD-VII), with considerable flood irrigation drainage (27%), and ISD-XI with considerable losses due to evaporation and wind drift in sprinkler irrigation systems (15%), brought down the average (IE_VII = 73%; IE_XI = 83%). Irrigation management was inadequate as there was a water deficit (WD) of 9%, partly affected by the 2005 drought (WD_{Apr-05/Sep-05} = 21%) and the low irrigation doses applied in ISD-XI (WD_XI = 12%).To sum up, intense re-use of water caused a water use index (percentage of water used by the crops) of 85% which surpassed 90% in periods of drought. Nevertheless, irrigation management should be improved in order to annul the water deficit and to maximize the productivity of the agrarian system.     

Assessment of irrigation and environmental quality at the hydrological basin level: I. Irrigation quality

Irrigated agriculture notably increases crop productivity, but consumes high volumes of water and may induce off-site pollution of receiving water bodies. The objectives of this paper were to diagnose the quality of irrigation and to prescribe recommendations aimed at improving irrigation management and reducing the off-site pollution from a 15,500 ha irrigation district located in the Ebro River Basin (Spain). Three hydrological basins were selected within the district where the main inputs (irrigation, precipitation, and groundwater inflows) and outputs (actual crop's evapotranspiration, surface drainage outflows, and groundwater outflows) of water were measured or estimated during a hydrological year. The highest volume of water (I = 1400 mm/year) was applied in the basin with highly permeable, low water retention, flood irrigated soils where 81% of the total surface was planted with alfalfa and corn. This basin had the lowest consumptive water use efficiency (CWUE = 45%), the highest water deficit (WD = 5%) and the highest drainage fraction (DF = 57%). In contrast, the lowest I (950 mm/year), the highest CWUE (62%), and the lowest WD (2%) and DF (37%) were obtained in the basin with 60% of the surface covered with deep, high water retention, alluvial valley soils, where 39% of the cultivated surface is sprinkler irrigated and with only 48% of the surface planted with alfalfa and corn. We concluded that the three most important variables determining the quality of irrigation and the volume of irrigation return flows in the studied basins were (i) soil characteristics, (ii) irrigation management and irrigation system, and (iii) crop water requirements. Therefore, the critical recommendations for improving the quality of irrigation are to (i) increase the efficiency of flood-irrigation, (ii) change to pressurized systems in the shallow and highly permeable soils, and (iii) reuse of drainage water for irrigation within the district. These management strategies will conserve water of high quality in the main reservoir and will decrease the crop water deficits and the volume of irrigation return flows, therefore, minimizing the off-site pollution from this irrigation district.     

Sprinkler evaporation losses in alfalfa during solid-set sprinkler irrigation in semiarid areas

Gross sprinkler evaporation losses (SEL_g) can be large and decrease irrigation application efficiency. However, it is not universally established how much of the SEL_g contributes to decrease the crop evapotranspiration during the sprinkler irrigation and how much are the net sprinkler losses (SEL_n). The components of SEL were the wind drift and evaporation losses (WDEL) and the water intercepted by the crop (IL). The gross WDEL (WDEL_g) and evapotranspiration (ET) were measured simultaneously in two alfalfa (Medicago sativa L.) plots, one being irrigated (moist, MT) and the other one not being irrigated (dry, DT). Catch can measurements, mass gains, and losses in the lysimeters and micrometeorological measurements were performed to establish net WDEL (WDEL_n) during the irrigation and net IL (IL_n) after the irrigation as the difference between ET_MT and ET_DT. Also, equations to estimate IL_n and net sprinkler evaporation losses (SEL_n) were developed. IL_n was strongly related to vapor pressure deficit (VPD). SEL_n were 8.3 % of the total applied water. During daytime irrigations, SEL_n was 9.8 % of the irrigation water and slightly less than WDEL_g (10.9 %). During nighttime irrigations, SEL_n were slightly greater than WDEL_g (5.4 and 3.7 %, respectively). SEL_n was mainly a function of wind speed.     

Irrigation modernization and water conservation in Spain: The case of Riegos del Alto Aragón

This study analyzes the effects of irrigation modernization on water conservation, using the Riegos del Alto Aragón (RAA) irrigation project (NE Spain, 123354 ha) as a case study. A conceptual approach, based on water accounting and water productivity, has been used. Traditional surface irrigation systems and modern sprinkler systems currently occupy 73% and 27% of the irrigated area, respectively. Virtually all the irrigated area is devoted to field crops. Nowadays, farmers are investing on irrigation modernization by switching from surface to sprinkler irrigation because of the lack of labour and the reduction of net incomes as a consequence of reduction in European subsidies, among other factors. At the RAA project, modern sprinkler systems present higher crop yields and more intense cropping patterns than traditional surface irrigation systems. Crop evapotranspiration and non-beneficial evapotranspiration (mainly wind drift and evaporation loses, WDEL) per unit area are higher in sprinkler irrigated than in surface irrigated areas. Our results indicate that irrigation modernization will increase water depletion and water use. Farmers will achieve higher productivity and better working conditions. Likewise, the expected decreases in RAA irrigation return flows will lead to improvements in the quality of the receiving water bodies. However, water productivity computed over water depletion will not vary with irrigation modernization due to the typical linear relationship between yield and evapotranspiration and to the effect of WDEL on the regional water balance. Future variations in crop and energy prices might change the conclusions on economic productivity.     

Wind effects on solid set sprinkler irrigation depth and yield of maize (<Emphasis Type="Italic">Zea mays</Emphasis>)

A field experiment was performed to study the effect of the space and time variability of water application on maize (Zea mays) yield when irrigated by a solid set sprinkler system. A solid set sprinkler irrigation layout, typical of the new irrigation developments in the Ebro basin of Spain, was considered. Analyses were performed (1) to study the variability of the water application depth in each irrigation event and in the seasonal irrigation and (2) to relate the spatial variability in crop yield to the variability of the applied irrigation and to the soil physical properties. The results of this research showed that a significant part of the variability in the Christiansen coefficient of uniformity (CU), and wind drift and evaporation losses were explained by the wind speed alone. Seasonal irrigation uniformity (CU of 88%) was higher than the average uniformity of the individual irrigation events (CU of 80%). The uniformity of soil water recharge was lower than the irrigation uniformity, and the relationship between both variables was statistically significant. Results indicated that grain yield variability was partly dictated by the water deficit resulting from the non-uniformity of water distribution during the crop season. The spatial variability of irrigation water depth when the wind speed was higher than 2 m s^–1 was correlated with the spatial variability of grain yield, indicating that a proper selection of the wind conditions is required in order to attain high yield in sprinkler-irrigated maize.     

Simple microirrigation techniques for improving irrigation efficiency on vegetable gardens

Microirrigation techniques can be used to improve irrigation efficiency on vegetable gardens by reducing soil evaporation and drainage losses and by creating and maintaining soil moisture conditions that are favourable to crop growth. Water balance experiments in Zimbabwe showed that over 50% of the water applied as surface irrigation on traditional irrigated gardens can be lost as soil evaporation. This result gives an indication of the potential improvement in irrigation efficiency that can be achieved by adopting irrigation methods that reduce soil evaporation at the same time as minimising losses due to drainage and canopy interception. During the period 1985 to 1995, irrigation trials and experiments were carried out in south-east Zimbabwe and northern Sri Lanka with the main aim of comparing and quantifying the benefits of using simple microirrigation techniques on traditional vegetable gardens. This paper reviews the results of these trials and experiments. Microirrigation techniques that were evaluated included low-head drip irrigation, pitcher irrigation and subsurface irrigation using clay pipes. Of these methods, subsurface irrigation using clay pipes was found to be particularly effective in improving yields, crop quality and water use efficiency as well as being cheap, simple and easy to use. The comparative advantages of subsurface irrigation were maintained for a range of crops grown under different climatic conditions. Good results were also obtained with subsurface irrigation when irrigation was carried out using with poor quality irrigation water.     

Long-term water balances in La Violada Irrigation District (Spain): II. Analysis of irrigation performance

The analysis of long-term irrigation performance series is a valuable tool to improve irrigation management and efficiency. This work focuses in the assessment of irrigation performance indices along years 1995-2008, and the cause-effect relationships with irrigation modernization works taking place in the 4000 ha surface-irrigated La Violada Irrigation District (VID). Irrigation management was poor, as shown by the low mean seasonal irrigation consumptive use coefficient (ICUC = 51%) and the high relative water deficit (RWD = 20%) and drainage fraction (DRF = 54%). April had the poorest irrigation performance because corn (with low water demand in this month) was irrigated to promote its emergence, whereas winter grains (with high water demands in this month) were not fully irrigated in water-scarce years. Corn, highly sensitive to water stress, was the crop with best irrigation performance because it was preferentially irrigated to minimize yield losses. The construction of a new elevated canal that decreased seepage and drainage fractions, the entrance in operation of six internal reservoirs that would increase irrigation scheduling flexibility, and the on-going transformation from surface to sprinkler irrigation systems are critical changes in VID that should lead to improved ICUC, lower RWD and lower DRF. The implications of these modernization works on the conservation of water quantity and quality within and outside VID is further discussed.     

Evaporation and drift losses from sprinkler irrigation systems under various operating conditions

Quantitative determinations of evaporation and drift losses from sprinkler systems were carried out under different operating conditions.Evaporation losses determined by an electrical-conductivity method ranged from 1.5 to 16.8% of the total sprinkled volume. Wind velocity and vapor pressure deficit were the most significant factors affecting the evaporation losses. Exponential relationships between the evaporation losses and both wind velocity and vapor pressure deficit have been found. For the operating pressures used in this study the least effect on evaporation was found.Drift losses measured by the magnesium-oxide method varied from 1.5 to 15.1%. Drift losses increased with the second power of the wind velocity, and decreased with increasing distance in the downwind direction.Combined losses from a sprinkler system for a given set of operating conditions have been estimated by using the results obtained from the experiments. Combined losses ranged from 1.7 to 30.7% of the applied water.     

Role of transpiration suppression by evaporation of intercepted water in improving irrigation efficiency

Sprinkler irrigation efficiency declines when applied water intercepted by the crop foliage, or gross interception (I_gross), as well as airborne droplets and ponded water at the soil surface evaporate before use by the crop. However, evaporation of applied water can also supply some of the atmospheric demands usually met by plant transpiration. Any suppression of crop transpiration from the irrigated area as compared to a non-irrigated area can be subtracted from I_gross irrigation application losses for a reduced, or net, interception (I_net) loss. This study was conducted to determine the extent in which transpiration suppression due to microclimatic modification resulting from evaporation of plant-intercepted water and/or of applied water can reduce total sprinkler irrigation application losses of impact sprinkler and low energy precision application (LEPA) irrigation systems. Fully irrigated corn (Zea Mays L.) was grown on 0.75 m wide east-west rows in 1990 at Bushland, TX in two contiguous 5-ha fields, each containing a weighing lysimeter and micrometeorological instrumentation. Transpiration (Tr) was measured using heat balance sap flow gauges. During and following an impact sprinkler irrigation, within-canopy vapor pressure deficit and canopy temperature declined sharply due to canopyintercepted water and microclimatic modification from evaporation. For an average day time impact irrigation application of 21 mm, estimated average I_gross loss was 10.7%, but the resulting suppression of measured Tr by 50% or more during the irrigation reduced I_gross loss by 3.9%. On days of high solar radiation, continued transpiration suppression following the irrigation reduced I_gross loss an additional 1.2%. Further 4–6% reductions in I_gross losses were predicted when aerodynamic and canopy resistances were considered. Irrigation water applied only at the soil surface by LEPA irrigation had little effect on the microclimate within the canopy and consequently on Tr or ET, or irrigation application efficiency.     

Comparison of sprinkler,trickle and furrow irrigation efficiencies for onion production

In the Mesilla Valley of southern New Mexico, furrow irrigation is the primary source of water for growing onions. As the demand for water increases, there will be increasing competition for this limited resource. Water management will become an essential practice used by farmers. Irrigation efficiency (IE) is an important factor into improving water management but so is economic return. Therefore, our objectives were to determine the irrigation efficiency, irrigation water use efficiency (IWUE) and water use efficiency (WUE), under sprinkler, furrow, and drip irrigated onions for different yield potential levels and to determine the IE associated with the amount of water application for a sprinkler and drip irrigation systems that had the highest economic return.Maximum IE (100%) and economic return were obtained with a sprinkler system at New Mexico State University’s Agriculture Science Center at Farmington, NM. This IE compared with the 54–80% obtained with the sprinkler irrigation used by the farmers. The IEs obtained for onion fields irrigated with subsurface drip irrigation methods ranged from 45 to 77%. The 45% represents the nonstressed treatments, in which an extra amount of irrigation above the evapotranspiration (Et) requirement was applied to keep the base of the onion plates wet. The irrigation water that was not used for Et went to deep drainage water. The return on the investment cost to install a drip system operated at a IE of 45 was 29%. Operating the drip system at a IE of 79% resulted in a yield similar to surface irrigated onions and consequently, it was not economical to install a drip system. The IEs at the furrow-irrigated onion fields ranged from 79 to 82%. However, the IEs at the furrow-irrigated onion fields were high because farmers have limited water resources. Consequently, they used the concept of deficit irrigation to irrigate their onion crops, resulting in lower yields. The maximum IWUE (0.084 t ha⁻¹ mm⁻¹ of water applied) was obtained using the sprinkler system, in which water applied to the field was limited to the amount needed to replace the onions’ Et requirements. The maximum IWUE values for onions using the subsurface drip was 0.059 and 0.046 t ha⁻¹ mm⁻¹ of water applied for furrow-irrigated onions. The lower IWUE values obtained under subsurface drip and furrow irrigation systems compared with sprinkler irrigation was due to excessive irrigation under subsurface drip and higher evaporation rates from fields using furrow irrigation. The maximum WUE for onions was 0.009 t ha⁻¹ mm⁻¹ of Et. In addition, WUE values are reduced by allowing the onions to suffer from water stress.     

Water demand and flows in the São Francisco River Basin (Brazil) with increased irrigation

Most activities that support economic growth in the São Francisco River Basin (Brazil) need water. Allocation of the water resources to each competing use needs quantification in order to develop an integrated water management plan. Irrigation agriculture is the largest water consuming activity in the basin. It has produced large economic and social advancements in the region and has potential for further development. The local development agency in the São Francisco River has projected an increase of more than 500,000 ha in irrigation developments distributed within the basin.Water requirements of the projected irrigation expansions and their effects on river flow were quantified. A semi-distributed model was constructed to simulate the water balance in 16 watersheds within the basin. The watersheds were hydrologically characterized by the average precipitation, atmospheric demand and runoff as well as their variability. Water requirements for increased irrigated agriculture were calculated using an agronomic mass balance. A Monte Carlo procedure generated the variability of irrigation requirements and resulting decreased river flows from the multidimensional probability distribution of the hydrologic variables of each watershed.Irrigation requirements were found to be more variable during the wet season because of weather variability. In contrast to what might be expected, in drier years, irrigation requirements were often larger during the wet season than in the dry season because the cropped area is largest in the wet months and variability of precipitation is greater. Increased irrigation shifted downward the distribution of river flows but not enough to affect other strategic water uses such as hydropower. Further irrigation expansion may be limited by wet season flows.     

Agro-environmental evaluation of irrigation land: II. Pollution induced by Bardenas Irrigation District (Spain)

It is difficult to quantify non-point contamination caused by irrigated agriculture. As continuation to the evaluation of water use on the scale of large irrigation districts, this second part seeks: (i) to quantify the mass of salt and nitrate exported by Bardenas Irrigation District included in the Arba basin (BID-Arba; 54,438 ha); (ii) to analyze the most influential factors; (iii) to propose agro-environmental contamination indices which can be incorporated into legislation.For this, salt and nitrate balances were carried out, assigning concentration values to each of the components of the water balance between 1 April 2004 and 30 September 2006. Saline and Nitrate Contamination Indices were also quantified which correct the mass of pollutants exported from irrigation return flows by geological and agronomic factors of the irrigation area studied.For the whole period of the study the exported mass of salt was 15 kg/(ha day), of which 65% came from geological materials in the area, 34% from irrigation water and only 1% from precipitation. As for exported nitrate, it was 76 g NO₃⁻-N/(ha day), only 25% of the quantities measured in other small basins (≈100 ha) of Bardenas district without re-use of drainage water for irrigation, but double the nitrate exported in other modern irrigation districts.Water and saline agro-environmental indices of BID-Arba resemble those of well-managed modern irrigation districts indicating little margin for improvement in water use and saline contamination. But, the nitrate-contamination-index was 1.5 times higher than well-managed modern irrigation districts indicating the necessity to change nitrogenous fertilization practices to minimize nitrate contamination.     

Irrigation with saline water: benefits and environmental impact

The shortage of water resources of good quality is becoming an important issue in the arid and semi-arid zones. For this reason the availability of water resources of marginal quality such as drainage water, saline groundwater and treated wastewater has become an important consideration. Nevertheless, the use of these waters in irrigated lands requires the control of soil salinity by means of leaching and drainage of excess water and salt. However, the leaching of salts, soil microelements and agro-chemicals can lower the quality of the drainage water in the irrigation scheme. The irrigation return flows with water or poor quality are a source of pollution of the surface water bodies situated downstream of the drainage outlet. Deep percolation could also contaminate the groundwater. Therefore, irrigation with saline water requires a comprehensive analysis even beyond the area where water is applied. The problem should be treated beyond the scope of the irrigation scheme, taking into consideration the groundwater and downstream surface water resources of the river basin. Consequently, the sustainable use of saline water in irrigated agriculture requires the control of soil salinity at the field level, a decrease in the amount of drainage water, and the disposal of the irrigation return flows in such a way that minimizes the side effects on the quality of downstream water resources. This paper describes the guidelines for a preliminary evaluation of the suitability of water for irrigation and the key factors for salinity control in lands irrigated with saline water. Options to improve the quality of the drainage water, strategies for the reuse of this water and alternatives for disposal of the outflow are also analysed. The final goal is to obtain sustainable agriculture and maintain the quality of the water resources in the river basin.     

Beyond irrigation efficiency

Parameters for accounting for water balance on irrigation projects have evolved over the past century. Development of the classic term irrigation efficiency is summarized along with recent modifications such as effective irrigation efficiency. The need for terms that describe measurable water balance components of irrigated agriculture is very important, as demands and competition for available renewable water supplies continue to increase with increasing populations. Examples of irrigation efficiency studies conducted during the past few decades are summarized along with related irrigation terminology. Traditional irrigation efficiency terminology has served a valid purpose for nearly a century in assisting engineers to design better irrigation systems and assisting specialists to develop improved irrigation management practices. It still has utility for engineers designing components of irrigation systems. However, newer irrigation-related terminology better describes the performance and productivity of irrigated agriculture. On a river-basin level, improved terminology is needed to adequately describe how well water resources are used within the basin. Brief suggestions for improving irrigation water management are presented.     

An economic perspective on the potential gains from improvements in irrigation water management

In recent years, several researchers have introduced new terms describing irrigation efficiency to enhance the information available when evaluating water policy alternatives. Some of the definitions expand the physical boundary considered when evaluating water use, while others account for the changes in water quality that occur as drainage water is reused in an irrigated area. While the concepts of basin, global, and effective efficiency have enhanced our understanding of water use in agriculture, public officials may derive incorrect policy implications when reviewing empirical estimates of those measures, particularly if information describing the economic impacts of water use and allocation decisions is not available. For example, some authors suggest that when estimates of basin-wide efficiency approach 100%, there is little opportunity to save water by improving water management and achieving higher levels of classical, farm-level efficiencies in upstream portions of an irrigated region. However, there may be significant opportunities to increase the net values generated with limited water resources by improving the distribution of water among farmers and reducing the negative, off-farm effects of irrigation and drainage activities. Economic analysis is helpful in identifying those opportunities and in designing policies that encourage farmers and water agency personnel to improve water management practices in ways that enhance social net benefits.     

Flow rate sprinkler development for site-specific irrigation

Due to the rapid depletion of water resources, water must be used more efficiently in agriculture to maintain current levels of yield in irrigated areas. The efficiency of irrigation systems can be increased by adjusting the amount of water applied to specific conditions of soil and crop, which may vary in a field. Taking into account spatial and temporal variability, it is evident that an equipment capable of providing different irrigation levels is necessary to meet the water requirement of the soil. This work aims to develop and evaluate a flow rate sprinkler to be used in center pivots or linear moving irrigation systems, with potential for utilization in irrigation scheduling. A prototype was developed by duplicating its calibrations, and discharge coefficient adjustment was carried out in the laboratory. To predict the flow rate, a successful model that represented the operation of the flow rate sprinkler was established. The calibration of the flow rate sprinkler prototype showed satisfactory statistical and technical results. Automation of the prototype was achieved by driving a step motor using communication from the parallel port of a microcomputer, which was controlled by a software developed for this purpose. The results were satisfactory and technically feasible.     

基于弹道理论有风条件下折射式喷头喷灌均匀度研究

为计算有风条件下折射式喷头水量分布及喷灌均匀度,以弹道轨迹理论为基础,依据风速分布模型,建立有风条件下折射式单喷头水量分布计算方法,采用该方法模拟出有风条件下Nelson D3000型喷头倒挂安装方式下水量分布特性,通过与实测资料进行对比,验证了模拟具有较高的准确度,可应用于有风条件下折射式喷头水量分布计算。在此基础上,选用4.76 mm(24号)喷嘴直径,模拟出不工况下单喷头水量分布,计算出组合情况下喷灌均匀度,分析了风速、风向、喷头间距、工作压力和安装高度5种因素对喷灌均匀度的影响,并对蒸发漂移损失进行了分析。结果表明:95%的置信区间下,喷头布置间距对喷灌均匀度的影响最显著,其次是安装高度和喷头工作压力,风速和风向对喷灌均匀度影响不显著。风速、喷头工作压力和安装高度都会对蒸发漂移损失产生影响,其中工作压力影响最大。当选用Nelson D3000型喷头在风速小于6 m/s的环境下喷灌时,应将喷头安装间距固定在2.13~3.04 m范围内。另外,该安装间距范围内,喷头安装高度和喷灌压力增大后,喷灌均匀度增大的效果不明显,因此应采用低压喷灌以降低喷灌系统运行成本;考虑到较高的喷头安装高度会产生较大的蒸发漂移损失,喷灌时还应适当降低喷头安装高度,以提高喷灌水分利用率。