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1.
S.L. Davis 《Agricultural Water Management》2010,98(1):19-28
Evapotranspiration-based irrigation controllers, also known as ET controllers, use ET information or estimation to schedule irrigation. Previous research has shown that ET controllers could reduce irrigation as much as 42% when compared to a time-based irrigation schedule. The objective of this study was to determine the capability of three brands of ET-based irrigation controllers to schedule irrigation compared to a theoretically derived soil water balance model based on the Irrigation Association Smart Water Application Technologies (SWAT) protocol to determine the effectiveness of irrigation scheduling. Five treatments were established, T1-T5, replicated four times for a total of twenty field plots in a completely randomized block design. The irrigation treatments were as follows: T1, Weathermatic SL1600 with SLW15 weather monitor; T2, Toro Intelli-sense; T3, ETwater Smart Controller 100; T4, a time-based treatment determined by local recommendations; and T5, a reduced time-based treatment 60% of T4. All treatments utilized rain sensors set at a 6 mm threshold. A daily soil water balance model was used to calculate the theoretical irrigation requirements for comparison with actual irrigation water applied. Calculated in 30-day running totals, irrigation adequacy and scheduling efficiency were used to quantify under- and over-irrigation, respectively. The study period, 25 May 2006 through 27 November 2007, was drier than the historical average with a total of 1326 mm of rainfall compared to 1979 mm for the same historical period. It was found that all treatments applied less irrigation than required for all seasons. Additionally, the ET controllers applied only half of the irrigation calculated for the theoretical requirement for each irrigation event, on average. Irrigation adequacy decreased when the ET controllers were allowed to irrigate any day of the week. All treatments had decreased scheduling efficiency averages in the rainy season with the largest decrease of 29 percentile points with a timer and rain sensor (T4) and an average decrease of 20 percentile points for the ET controllers, indicating that site specific rainfall has a significant effect on scheduling efficiency results. Rainfall did not drastically impact the average irrigation adequacy results. For this study, there were two controller program settings that impacted the results. The first setting was the crop coefficients where specific values were chosen for the location of the study when calculating the theoretical requirement whereas the controllers used default values. The second setting was the soil type that defines the soil water holding capacity of the soil. The ET controllers were able to regularly adjust to real-time weather, unlike the conventional irrigation timers. However, the incorporation of site specific rainfall measurements is extremely important to their success at managing landscape water needs and at a minimum a rain sensor should be used. 相似文献
2.
A variety of technologies for reducing residential irrigation water use are available to homeowners. These “Smart Irrigation” technologies include evapotranspiration (ET)-based controllers and soil moisture sensor (SMS) controllers. The purpose of this research was to evaluate the effectiveness of these technologies, along with rain sensors, based on irrigation applied and turfgrass quality measurements on St. Augustinegrass (Stenotaphrum secundatum (Walter) Kuntze). Testing was performed on two types of SMS controllers (LawnLogic LL1004 and Acclima Digital TDT RS500) at three soil moisture threshold settings. Mini-Clik rain sensors (RS) comprised six treatments at two rainfall thresholds (3 mm and 6 mm) and three different irrigation frequencies (1, 2, and 7 d/wk). Two ET controllers were also tested, the Toro Intelli-Sense controller and the Rain Bird ET Manager. A time-based treatment with 2 days of irrigation per week without any type of sensor (WOS) to bypass irrigation was established as a comparison. All irrigation controller programming represented settings that might be used in residential/commercial landscapes. Even though three of the four testing periods were relatively dry, all of the technologies tested managed to reduce water application compared to the WOS treatment, with most treatments also producing acceptable turf quality. Reductions in irrigation applied were as follows: 7–30% for RS-based treatments, 0–74% for SMS-based treatments, and 25–62% for ET-based treatments. The SMS treatments at low threshold settings resulted in high water savings, but reduced turf quality to unacceptable levels. The medium threshold setting (approximately field capacity) SMS-based treatment produced good turfgrass quality while reducing irrigation water use compared to WOS by 11–53%. ET controllers with comparable settings and good turf quality had −20% to 59% savings. Reducing the irrigation schedule (treatment DWRS) by 40% and using a rain sensor produced water savings between 36% and 53% similar to smart controllers. Proper installation and programming of each of the technologies was essential element to balancing water conservation and acceptable turf quality. Water savings with the SMS controllers could have been increased with a reduced time-based irrigation schedule. Efficiency settings of 100% (DWRS) and 95% (TORO) did not reduce turf quality below acceptable limits and resulted in substantial irrigation savings, indicating that efficiency values need not be low in well designed and maintained irrigation systems. For most conditions in Florida, the DWRS schedule (60% of schedule used for SMS treatments) can be used with either rain sensors or soil moisture sensors in bypass control mode as long as the irrigation system has good coverage and is in good repair. 相似文献
3.
利用气象资料指导膜下滴灌棉花灌溉的试验研究 总被引：9，自引：1，他引：8
利用气象资料指导膜下滴灌棉花灌溉的试验于2007年5~10月份在新疆生产建设兵团灌溉中心试验站的试验基地进行。试验共设置7个处理,分别按生育期ET0的不同比例进行灌水。试验结果表明,为了获得经济合理的产量,膜下滴灌棉花全生育期耗水量应控制在360~405 mm之间。用实时气象资料指导膜下滴灌棉花的灌溉具有很好的可行性,蕾期和花铃后期10 d灌1次水,灌水定额为60%ET0;花铃前期7 d灌1次水,灌水定额为75%ET0,是一种适宜北疆地区膜下滴灌棉花的灌水模式。 相似文献
4.
About half of the total fresh water used for irrigation in Asia is used for rice production. Decreasing water resources and increasing water costs necessitates increasing water use efficiency for rice. The most common method of irrigation in northwestern India is through alternate wetting and drying with a fixed irrigation interval, irrespective of soil type and climatic demand resulting in over-irrigation or under-irrigation under different soil and weather situations. Soil matric potential may be an ideal criterion for irrigation, since variable atmospheric evaporativity, soil texture, cultural practices and water management affect rice irrigation water requirements. A 4-year field study was conducted to assess the feasibility of rice irrigation scheduling on the basis of soil matric potential and to determine the optimum matric potential so as to optimize irrigation water without any adverse effect on the yield. The treatments included scheduling irrigation to rice with tensiometers installed at 15–20 cm soil depth at five levels of soil matric suction viz. 80, 120, 160, 200 and 240±20 cm, in addition to the recommended practice of alternate wetting and drying with an interval of 2 days after complete infiltration of ponded water. The grain yield of rice remained unaffected up to soil moisture suction of 160±20 cm each year. Increasing soil matric suction to 200 and 240±20 cm decreased rice grain yield non-significantly by 0–7% and 2–15%, respectively, over different years compared to the recommended practice of the 2-day interval for scheduling irrigation. Irrigation at 160±20 cm soil matric suction helped save 30–35% irrigation water compared to that used with the 2-day interval irrigation. With a soil matric potential irrigation criterion the total amount of irrigation water used was a function of the number of rainy days and evaporation during the rice season. 相似文献
5.
Landscape irrigation by evapotranspiration-based irrigation controllers under dry conditions in Southwest Florida 总被引：1，自引：0，他引：1
Due to high demand for aesthetically pleasing urban landscapes from continually increasing population in Florida, new methods must be explored for outdoor water conservation. Three brands of evapotranspiration (ET) controllers were selected based on positive water savings results in arid climates. ET controllers were evaluated on irrigation application compared to a time clock schedule intended to mimic homeowner irrigation schedules. Three ET controllers were tested: Toro Intelli-sense; ETwater Smart Controller 100; Weathermatic SL1600. Other time-based treatments were TIME, based on the historical net irrigation requirement and RTIME that was 60% of TIME. Each treatment was replicated four times for a total of twenty St. Augustinegrass plots which were irrigated through individual irrigation systems. Treatments were compared to each other and to a time-based schedule without rain sensor (TIME WORS) derived from TIME. The study period, August 2006 through November 2007, was dry compared to 30-year historical average rainfall. The ET controllers averaged 43% water savings compared to a time-based treatment without a rain sensor and were about twice as effective and reducing irrigation compared to a rain sensor alone. There were no differences in turfgrass quality across all treatments over the 15-month study. The controllers adjusted their irrigation schedules to the climatic demand effectively, with maximum savings of 60% during the winter 2006-2007 period and minimum savings of 9% during spring 2007 due to persistent dry conditions. RTIME had similar savings to the ET controllers compared to TIME WORS indicating that proper adjustment of time clocks could result in substantial irrigation savings. However, the ET controllers would offer consistent savings once programmed properly. 相似文献
6.
Nicole A. Dobbs Kati W. Migliaccio Yuncong Li Michael D. Dukes Kelly T. Morgan 《Irrigation Science》2014,32(3):193-203
Irrigation technologies [i.e., automatic timer, automatic timer with rain sensor, automatic timer with soil water sensor (SWS), and evapotranspiration (ET) controller] were compared in a bahiagrass plot study by measuring irrigation applied, water volumes drained, and NO3–N and NH4–N leached. All irrigation technologies were scheduled to irrigate on Sunday and Thursday. Three different irrigation depths were evaluated with the automatic timer: 15, 19, and 32 mm. SWS treatment allowed scheduled irrigation if soil water content was estimated to be below 70 % of water holding capacity, while the ET treatment allowed scheduled irrigation if soil water content was estimated to be below 50 % of plant available water. The rain sensor, SWS, and ET controller treatments applied significantly less water (p < 0.05) than the automatic timer treatment (which irrigates on specific days and times without regard to system conditions), reducing water by 17–49, 64–75, and 66–70 %, respectively. NO3–N and NH4–N were only significantly different after the second fertilizer application, which coincided with the 32 mm per event irrigation rate for the automatic timer treatment. Under these conditions, the automatic timer treatment had significantly greater NO3–N and NH4–N leachate than other treatments due to greater occurrence of soil water content exceeding water holding capacity, which resulted in drainage. Findings suggest that water can be saved using rain sensors, SWSs, or ET controllers and that leachate NO3–N and NH4–N can be reduced using rain sensors, SWSs, or ET controllers. 相似文献
7.
Integrating satellite-based evapotranspiration with simulation models for irrigation management at the scheme level 总被引：2，自引：2，他引：0
Improvements in irrigation management are urgently needed in regions where water resources for irrigation are being depleted.
This paper combines a water balance model with satellite-based remote-sensing estimates of evapotranspiration (ET) to provide
accurate irrigation scheduling guidelines for individual fields. The satellite-derived ET was used in the daily soil water
balance model to improve accuracy of field-by-field ET demands and subsequent field-scale irrigation schedules. The combination
of satellite-based ET with daily soil water balance incorporates the advantages of satellite remote-sensing and daily calculation
time steps, namely, high spatial resolution and high temporal resolution. The procedure was applied to Genil–Cabra Irrigation
Scheme of Spain, where irrigation water supply is often limited by regional drought. Compared with traditional applications
of water balance models (i.e. without the satellite-based ET), the combined procedure provided significant improvements in
irrigation schedules for both the average condition and when considering field-to-field variability. A 24% reduction in application
of water was estimated for cotton if the improved irrigation schedules were followed. Irrigation efficiency calculated using
satellite-based ET and actual applied irrigation water helped to identify specific agricultural fields experiencing problems
in water management, as well as to estimate general irrigation efficiencies of the scheme by irrigation and crop type. Estimation
of field irrigation efficiency ranged from 0.72 for cotton to 0.90 for sugar beet. 相似文献
8.
Haijun Liu Lipeng Yu Yu Luo Xiangping Wang Guanhua Huang 《Agricultural Water Management》2011,98(4):483-492
The North China Plain (NCP) is one of the main productive regions for winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.) in China. However, water-saving irrigation technologies (WSITs), such as sprinkler irrigation technology and improved surface irrigation technology, and water management practices, such as irrigation scheduling have been adopted to improve field-level water use efficiency especially in winter wheat growing season, due to the water scarcity and continuous increase of water in industry and domestic life in the NCP. As one of the WSITs, sprinkler irrigation has been increasingly used in the NCP during the past 20 years. In this paper, a three-year field experiment was conducted to investigate the responses of volumetric soil water content (SWC), winter wheat yield, evapotranspiration (ET), water use efficiency (WUE) and irrigation water use efficiency (IWUE) to sprinkler irrigation regimes based on the evaporation from an uncovered, 20-cm diameter pan located 0-5 cm above the crop canopy in order to develop an appropriate sprinkler irrigation scheduling for winter wheat in the NCP. Results indicated that the temporal variations in SWC for irrigation treatments in the 0-60-cm soil layer were considerably larger than what occurred at deeper depths, whereas temporal variations in SWC for non-irrigation treatments were large throughout the 0-120-cm soil layer. Crop leaf area index, dry biomass, 1000-grains weight and yield were negatively affected by water stress for those treatments with irrigation depth less than 0.50E, where E is the net evaporation (which includes rainfall) from the 20-cm diameter pan. While irrigation with a depth over 1.0E also had negative effect on 1000-grains weight and yield. The seasonal ET of winter wheat was in a range of 206-499 mm during the three years experiments. Relatively high yield, WUE and IWUE were found for the irrigation depth of 0.63E. Therefore, for winter wheat in the NCP the recommended amount of irrigation to apply for each event is the total 0.63E that occurred after the previous irrigation provided total E is in a range of 30-40 mm. 相似文献
9.
在2个灌水水平下（I1：高水,I2：低水）以不同滴灌带间距（A1：1m,A2：0.5m）与覆膜方式（M1：全膜覆盖,M2：半膜覆盖）进行2a田间试验,结合作物产量、作物水分利用效率（WUE）以及产投比筛选适宜的膜下滴灌模式,并利用产量水分敏感系数（ky）确定最优的膜下滴灌模式。结果表明：在低频灌溉模式下,部分覆膜处理的蒸腾（ET）高于全覆膜处理,而产量和WUE低于全覆膜处理。尽管滴灌带间距对ET的影响不明显,然而在高水处理下,“一管单行”作物的产量与WUE高于“一管双行”。高频灌溉模式下,作物产量及WUE对灌溉量、覆膜方式、滴灌带间距的响应呈现耦合性。低频灌溉条件下,ky对灌溉量及滴灌带间距的响应均不显著,而部分覆盖处理WUE低,ky高,对水分胁迫的响应敏感。高频灌溉条件下,覆膜方式、灌溉量以及滴灌带间距均对ky 产生影响。高频灌溉条件下,ky能对经WUE筛选出的膜下滴灌处理进行进一步的优选。基于ky的结果,结合产量、水分利用效率与产投比,建议在高频灌溉条件下采取“全膜低水+一管双行”模式或“半膜高水+一管单行”模式,在低频灌溉条件下采取全膜高水模式。 相似文献
10.
Kamal H. Amer 《Agricultural Water Management》2010,97(10):1553-1206
Non-uniformity of water distribution under irrigation system creates both deficit and surplus irrigation areas. Water salinity can be hazard on crop production; however, there is little information on the interaction of irrigation and salinity conditions on corn (Zea Mays) growth and production. This study evaluated the effect of salinity and irrigation levels on growth and yield of corn grown in the arid area of Egypt. A field experiment was conducted using corn grown in northern Egypt at Quesina, Menofia in 2009 summer season to evaluate amount of water applied, salinity hazard and their interactions. Three salinity levels and five irrigation treatments were arranged in a randomized split-plot design with salinity treatments as main plots and irrigation rates within salinity treatments. Salinity treatments were to apply fresh water (0.89 dS m−1), saline water (4.73 dS m−1), or mixing fresh plus saline water (2.81 dS m−1). Irrigation treatments were a ratio of crop evapotranspiration (ET) as: 0.6ET, 0.8ET, 1.0ET, 1.2ET, and 1.4ET. In well-watered conditions (1.0ET), seasonal water usable by corn was 453, 423, and 380 mm for 0.89EC, 2.81EC and 4.73EC over the 122-day growing season, respectively. Soil salt accumulation was significantly increased by either irrigation salinity increase or amount decrease. But, soil infiltration was significantly decreased by either salinity level or its interaction with irrigation amount. Leaf temperature, transpiration rate, and stomata resistance were significantly affected by both irrigation and salinity levels with interaction. Leaf area index, harvest index, and yield were the greatest when fresh and adequate irrigation was applied. Grain yield was significantly affected in a linear relationship (r2 ≥ 0.95) by either irrigation or salinity conditions with no interaction. An optimal irrigation scheduling was statistically developed based on crop response for a given salinity level to extrapolate data from the small experiment (uniform condition) to big field (non-uniformity condition) under the experiment constraints. 相似文献
11.
Irrigation frequency is one of the most important factors in drip irrigation scheduling, and a proper irrigation frequency
can establish moderate moist and oxygen conditions in the root zone throughout the crop period. Field experiments on the effects
of irrigation frequency on radish growth and water use were carried out in 2001 and 2002. The experiment included six irrigation
frequencies: once every day, once every 2 days, once every 3 days, once every 4 days, once every 6 days and once every 8 days.
There was no significant difference among the six treatments on radish development and yield, but significant differences
in radish roots distribution and market quality were found. Radishes irrigated once every 3 days had well-developed roots
throughout the crop period, the lowest cracking rate and the least number of radishes of Grade 3. The observation results
of lysimeter in 2002 showed that radish evapotranspiration decreased as irrigation frequency decreased, and the general changing
tendency of 2-day ET of high irrigation frequency was related to that of 2-day evaporation. It is recommended that radish
irrigation frequency should be once every 3 days and the irrigation amount should be estimated according to the evaporation
of 20 cm diameter pan in the North China Plain. 相似文献
12.
Nicholas Kiggundu Kati W. Migliaccio Bruce Schaffer Yuncong Li Jonathan H. Crane 《Irrigation Science》2012,30(4):275-286
This project was designed to determine the effect of fertilizer rate and irrigation scheduling on water use, nutrient leaching, and fruit yield of young avocado trees (Persea americana Mill. cv. Simmonds). Seven nutrient and irrigation management practices were evaluated: (1) irrigation based on crop evapotranspiration (ET) with 50% fertilizer at a standard rate (FSR); (2) ET irrigation with FSR (typical for avocado production in the area); (3) ET irrigation with 200% FSR; (4) irrigation based on exceedance of 15-kPa (SW) soil water suction with 50% FSR; (5) SW with FSR; (6) SW with 200% FSR; and (7) irrigation at a set schedule (based on timing and frequency typically used in local avocado production) with FSR. The SW with FSR treatment saved 87% of the water volume applied and reduced total phosphorus leached by 74% compared to the set schedule irrigation with FSR. The SW with FSR treatment had higher avocado fruit production, tree water-use efficiency, and fertilizer-use efficiency than the other six treatments. Thus, the use of soil water monitoring for irrigation management can substantially increase sustainability of young avocado orchards in southern Florida. 相似文献
13.
Field experiment was carried out to investigate the effect of soil matric potential (SMP) on tomato yield, evapotranspiration (ET), water use efficiency (WUE) and irrigation water use efficiency (IWUE) under drip irrigation condition in North China Plain. The experiment included five treatments, which controlled SMP at 0.2 m depth immediately under drip emitter higher than −10 (S1), −20 (S2), −30 (S3), −40 (S4) and −50 kPa (S5), respectively, after tomato plant establishment. The results showed that different SMP affected irrigation amount and tomato ET. Irrigation amount decreased from 185 mm (S1) to 83.6 mm (S5) in 2004, and from 165 mm (S1) to 109 mm (S5) in 2005, respectively. The ET decreased from 270 mm (S1) to 202 mm (S5) in both years. However, it was found that SMP did not affect the tomato yield significantly, for the range of SMP investigated. Both WUE and IWUE increased as SMP decreased. The maximum WUE (253 and 217 kg/ha mm) and IWUE (620 and 406 kg/ha mm) were for S5 in 2 years, whereas the minimum WUE (178 and 155 kg/ha mm) and IWUE 261 and 259 kg/ha mm) were for S1 in 2004 and 2005. Based on the above results, therefore, it is recommended that if the tomatoes are well irrigated (SMP is higher than −20 kPa) during establishment, controlling SMP higher than −50 kPa at 0.2 m depth immediately under drip emitter can be used as an indicator for drip irrigation scheduling during following period of tomato growth in North China Plain. 相似文献
14.
Santiago Bonachela Alicia María González María Dolores Fernández 《Irrigation Science》2006,25(1):53-62
Irrigation scheduling based on the daily historical crop evapotranspiration (ETh) data was theoretically and experimentally assessed for the major soil-grown greenhouse horticultural crops on the Almería coast in order to improve irrigation efficiency. Overall, the simulated seasonal ETh values for different crop cycles from 41 greenhouses were not significantly different from the corresponding values of real-time crop evapotranspiration (ETc). Additionally, for the main greenhouse crops on the Almería coast, the simulated values of the maximum cumulative soil water deficit in each of the 15 consecutive growth cycles (1988–2002) were determined using simple soil-water balances comparing daily ETh and ETc values to schedule irrigation. In most cases, no soil-water deficits affecting greenhouse crop productivity were detected, but the few cases found led us to also assess experimentally the use of ETh for irrigation scheduling of greenhouse horticultural crops. The response of five greenhouse crops to water applications scheduled with daily estimates of ETh and ETc was evaluated in a typical enarenado soil. In tomato, fruit yield did not differ statistically between irrigation treatments, but the spring green bean irrigated using the ETh data presented lower yield than that irrigated using the ETc data. In the remaining experiments, the irrigation-management method based on ETh data was modified to consider the standard deviation of the inter-annual greenhouse reference ET. No differences between irrigation treatments were found for productivity of pepper, zucchini and melon crops. 相似文献
15.
D. J. Undersander 《Irrigation Science》1987,8(1):23-33
Summary Four cultivars of alfalfa (Medicago sativa L cv. Vangard, Cody, Zia, and Dawson) were grown under a gradient irrigation system on a Pullman clay loam soil (fine, mixed, thermic, Torrertic Paleustoll) at Bushland, Texas. Twelve harvests were taken during 1983, 1984 and 1985 over a wide range of irrigation levels. Alfalfa was harvested at 10% bloom and subsamples were oven dried and ashed. Irrigation water and rainfall were determined by catchment collections and soil moisture content was determined with a neutron soil moisture probe. Potential evaporation was determined by pan evaporation and by modified Penman, Priestley and Taylor, and Jensen and Haise prediction equations from climatic data. No varietal differences in the relationship of yield to water or water use efficiency occurred. Yield within each harvest correlated well with evapotranspiration (ET). The regression of yield with ET over all twelve harvests had a low coefficient of determination. Relative yield had a high correlation with relative ET when maximum ET was measured but the correlation was lower when maximum ET was calculated from a prediction equation or pan evaporation. The correlation increased when the maximum yield for each harvest was used rather than a constant value. Including a high temperature factor in the equation greatly improved the correlation between yield and ET but the correlation was not as high as when relative yield was correlated with relative measured ET. Water use efficiency was highest with the highest yields.Contribution Texas Agricultural Experiment Station. Paper No. 20929 相似文献
16.
Summary Investigations were carried out in 1989 to determine the evapotranspiration (ET) of alfalfa when irrigated with saline waste water coming from the evaporation of fresh water in the cooling towers of Utah Power and Light Company Electrical Power Plant at Huntington in central Utah, U.S.A. The primary goal is to dispose of the waste water from the power plant by irrigation and to maximize salt deposition in the soil, maximize crop ET, minimize runoff from the soil surface, and minimize leaching to the ground water. Using the Bowen ratio-energy balance method, alfalfa evapotranspiration was measured at an experimental site for each 20-minute period during the 1989 irrigation season. Using a simplified seasonal water balance, the results showed that cumulative irrigation plus rain was less than evapotranspiration for the 1989 irrigation season. This means that for the long term in addition to irrigation and precipitation some water was withdrawn from the soil for alfalfa crop water requirements (ETa). Short term evaluations showed that because of unforeseen heavy rain (thunder showers) in this mountainous area between irrigations, ETa was occasionally less than irrigation plus rain. This means the excess water was stored in the soil for later use. The average value for ETa/ETp (potential ET) for the 1989 irrigation season was 0.47 but occasionally the ratio was greater than unity. Short-term studies (Hanks et al. 1990 a) indicate that yield and ETa are likely to decrease only slightly for the coming years if saline irrigation water is applied. This method of investigation can be applied to any industrial processes which produce waste water. 相似文献
17.
Evapotranspiration data assimilation with genetic algorithms and SWAP model for on-demand irrigation 总被引：3，自引：1，他引：2
Evapotranspiration (ET) is one of the indicators of water use efficiency. Periodic information of ET based on remote sensing
is useful for an on-demand irrigation (ODI) management. The main objective of this paper was to develop an ET data assimilation
scheme to optimize the parameters of an agro-hydrology model for ODI scheduling. The soil, water, atmosphere, and plant (SWAP)
simulation model has been utilized for this purpose. We computed remote sensing-based ET for a wheat field in the Sirsa Irrigation
Circle, Haryana, in India using 18 cloud-free moderate resolution imaging spectroradiometer images taken between December
2001 and April 2002. The surface energy balance algorithm for land (SEBAL) was used for this purpose. Because ET estimates
from SEBAL provide information on the surface soil moisture state, they were treated as observations to estimate unknown parameters
of the SWAP model via a stochastic data assimilation (genetic algorithm) approach. The SWAP parameters were optimized by minimizing
the residuals between SEBAL and SWAP model-based ET values. The optimized parameters were used as input to SWAP to estimate
soil water balance for ODI scheduling. The results showed that the selected parameters (i.e. sowing, harvesting, and irrigation
scheduling dates) were successfully estimated with the data assimilation methodology. The SWAP model produced reasonable states
of water balance by assimilating ET observations. The root mean square of error was 0.755 and 2.132 cm3/cm3 for 0–15 and 15–30 cm soil depths the same layers, respectively. With optimized parameters for ODI, SWAP predicted higher
yield and water use efficiency than traditional farmer’s irrigation criteria. The data assimilation methodology produced can
be considered as an operational tool at the field scale to schedule irrigation or predict irrigation requirements from remote
sensing-based ET. 相似文献
18.
河套灌区玉米农田蒸散动态变化及其影响因子的通径分析 总被引：1，自引：0，他引：1
采用大型称重式蒸渗仪研究了内蒙古河套灌区玉米蒸散动态规律,并运用通径分析法探讨了玉米蒸散量ET与各影响因子间的相关关系.结果表明:充分灌溉处理下玉米生育期(播前-收获)累积蒸散量为593.72 mm,亏缺灌溉处理下为395.21 mm,日平均蒸散量分别为4.24和2.82 mm/d.由各生育期的分布情况可知苗期蒸散量最小,分别占全生育期的3.7%和5.8%;拔节期开始,蒸散量逐渐增大,在抽雄期达到峰值,2种处理总蒸散量分别为279.38和166.76 mm,日平均蒸散量分别为8.47和5.05 mm/d,分别占整个生育期蒸散总量的47.1%和42.2%.由小时尺度蒸散量变化规律可知,玉米日蒸散量变化规律表现为早晚低、中午高的“单峰型”曲线特征.通径分析表明:2种灌溉处理下,饱和水气压和平均气温对ET的综合决定能力较大,是2个主要的环境驱动因子;2种灌溉处理下对蒸散作用最小的因子均为风速,且风速对ET的影响以间接作用为主.影响河套灌区玉米蒸散的主要气象因子为饱和水气压与气温. 相似文献
19.
为快速准确估算农田蒸散量,利用24个群集式蒸渗仪,在国家节水灌溉北京工程技术研究中心大兴节水灌溉试验站进行了两年的灌溉试验,获得冬小麦-夏玉米生育期的日内冠气温差和实际日蒸散量(ET_a)等数据,对不同水分处理下的S-I蒸散量估算模型进行率定及验证,并分析模型特征参数a、b的变化规律及两者的差异。结果表明:冬小麦的S-I模型特征参数a在日间随时间变化先增大、后减小,在严重水分胁迫处理时a为负值、且数值较小,其余灌溉处理时参数a由正值逐渐变化至负值;不同灌水处理b均为负值,充分灌溉处理时b在日间随时间变化逐渐增大,严重水分胁迫处理时b相对较大,日间变化趋势不稳定。水分胁迫对夏玉米模型参数的影响程度低于冬小麦,特征参数a均为正值,参数b均为负值,且随时间变化逐渐增大;水分胁迫处理时b变化范围明显小于其他两个处理,干旱处理特征参数日间变化较大。冬小麦与夏玉米不同处理之间模型参数a、b变化差异较大,但冠层温度和空气温度差T_c-T_a与日蒸散量和日净辐射量差ET_d-Rn_d间拟合精度都在13:00时最高,此时充分灌溉冬小麦和夏玉米的模型参数a、b分别为1.082、-1.127和1.588、-1.363。利用率定的S-I模型计算冬小麦和夏玉米主要生育期ET_d与实测ET_a之间的决定系数R~2均在0.7以上,均方根误差RMSE均小于0.89 mm/d,一致性系数d均在0.9以上。尤其是充分灌溉处理的数据间R~2和d均较高,RMSE小于其他处理,说明水分胁迫影响模型的估算精度,S-I模型能够更准确地估算水分胁迫较少农田的蒸散量。 相似文献