The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Ping Guo - One of the best experts on this subject based on the ideXlab platform.
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simulation and optimization for crop water allocation based on crop water production functions and climate factor under uncertainty
Applied Mathematical Modelling, 2013Co-Authors: Fangfang Tong, Ping GuoAbstract:Abstract In this paper, the uncertainty methods of interval and functional interval are introduced in the research of the uncertainty of crop water production function itself and optimal allocation of water resources in the Irrigation area. The crop water production functions in the whole growth period under uncertainty and the optimal allocation of water resources model in the Irrigation area under uncertainty are established, and the meteorological factor is considered in the model. It can promote the practical application of the uncertain methods, reflect the complexity and uncertainty of the actual situation, and provide more reliable scientific basis for using water resources economically, fully improving Irrigation Efficiency, and keeping the sustainable development of the irrigated area. This approach has important value on theoretical and practical for the optimal Irrigation schedule, and has very broad prospects for research and development to other related agriculture water management.
Nicholas Dercas - One of the best experts on this subject based on the ideXlab platform.
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investigating the effects of soil moisture sensors positioning and accuracy on soil moisture based drip Irrigation scheduling systems
Agricultural Water Management, 2015Co-Authors: Konstantinos X. Soulis, S Elmaloglou, Nicholas DercasAbstract:Recent advances in electromagnetic sensor technologies have made automated Irrigation scheduling a reality using state-of-the-art soil moisture sensing devices. However, many of the available guidelines for sensor placement were empirically determined from site and crop specific experiments. Sensors accuracy could be also an important factor affecting Irrigation Efficiency. This study investigates how soil moisture sensors positioning and accuracy may affect the performance of soil moisture based surface drip Irrigation scheduling systems under various conditions. For this purpose several numerical experiments were carried out using a mathematical model, incorporating a system-dependent boundary condition in order to simulate soil moisture based Irrigation scheduling systems. The results of this study provided clear evidence that soil moisture sensors positioning and accuracy may considerably affect Irrigation Efficiency in soil moisture based drip Irrigation scheduling systems. In specific cases the effect of soil moisture sensors positioning was as high as 16%; however, when nearby sensor positions were examined, the observed differences were generally low. The effect of sensors accuracy was even clearer. For the lower sensor's error level studied (±0.01cm3cm−3) the effect on Irrigation Efficiency ranged between 2.5% and 6.4%, while for the higher error level (±0.03cm3cm−3) the effect ranged between 10.2% and 18.7%. These results highlight the importance of a detailed study taking into account the characteristics of specific crops, Irrigation, and scheduling systems as well as soil moisture sensors in order to provide a sound basis for improved Irrigation scheduling. The need for soil specific calibration of the sensors used in such systems is highlighted as well. Lastly, a significant outcome of this study is the ability of computer models to serve as efficient tools for the detailed investigation of sensors positioning and accuracy, or other automated scheduling system characteristics.
Marvin E. Jensen - One of the best experts on this subject based on the ideXlab platform.
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Beyond Irrigation Efficiency
Irrigation Science, 2007Co-Authors: Marvin E. JensenAbstract:Parameters for accounting for water balance on Irrigation projects\nhave evolved over the past century. Development of the classic term\nIrrigation Efficiency is summarized along with recent modifications\nsuch as effective Irrigation Efficiency . The need for terms that\ndescribe measurable water balance components of irrigated agriculture\nis very important, as demands and competition for available renewable\nwater supplies continue to increase with increasing populations.\nExamples of Irrigation Efficiency studies conducted during the past\nfew decades are summarized along with related Irrigation terminology.\nTraditional Irrigation Efficiency terminology has served a valid\npurpose for nearly a century in assisting engineers to design better\nIrrigation systems and assisting specialists to develop improved\nIrrigation management practices. It still has utility for engineers\ndesigning components of Irrigation systems. However, newer Irrigation-related\nterminology better describes the performance and productivity of\nirrigated agriculture. On a river-basin level, improved terminology\nis needed to adequately describe how well water resources are used\nwithin the basin. Brief suggestions for improving Irrigation water\nmanagement are presented.
Christopher Martius - One of the best experts on this subject based on the ideXlab platform.
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a gis based approach for up scaling capillary rise from field to system level under soil crop groundwater mix
Irrigation Science, 2014Co-Authors: Usman Khalid Awan, Bernhard Tischbein, Christopher MartiusAbstract:Capillary rise represents an often neglected fraction of the water budget that contributes to crop water demand in situations of shallow groundwater levels. Such a situation is typical in irrigated areas of Central Asia where water from capillary rise is exploited by farmers to meet production targets in Uzbekistan under uncertain water supply. This leads to higher water inputs than needed and creates a vicious cycle of salinization that ultimately degrades the agricultural land. In this study, capillary rise is quantified at different spatial scales in the Shomakhulum Water Users Association (WUA), situated in the southwest of Khorezm, Uzbekistan. The mathematical model HYDRUS-1D was used to compute the capillary rise at field level for three major crops (cotton, wheat and vegetables) on six different hydrological response units (HRUs). These six HRUs having homogenous groundwater levels (1–2 m beneath the soil surface) and soil texture were created using GIS and remote-sensing techniques. Capillary rise from these HRU was then up-scaled to WUA level using a simple aggregation approach. The groundwater levels simulated by FEFLOW-3D model for these HRUs in a parallel study under four improved Irrigation Efficiency scenarios (S-A: current Irrigation Efficiency or business-as-usual, S-B: improved conveyance Efficiency, S-C: increased application Efficiency and S-D: improved conveyance and application Efficiency) were then introduced into HYDRUS-1D to quantify the impact of improved efficiencies on the capillary rise contribution. Results show that the HRUs with shallow groundwater-silt loam (S-SL), medium groundwater-silt loam (M-SL) and deep groundwater-silty clay loam (D-SCL) have capillary rise contribution of 28, 23 and 16 % of the cotton water requirements, 12, 5 and 0 % of the vegetable water requirements and 9, 6 and 0 % for the wheat water requirements, respectively. Results of the scenarios for the whole WUA show that the maximum capillary rise contribution (19 %) to the average of all crops in the WUA was for the S-A scenario, which reduced to 17, 11 and 9 % for S-B, S-C and S-D, respectively. Therefore, it is recommended that before any surface water intervention or drainage re-design, water managers should be informed about the impacts on groundwater hydrology and hence should adopt appropriate strategies.
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combining hydrological modeling and gis approaches to determine the spatial distribution of groundwater recharge in an arid Irrigation scheme
Irrigation Science, 2013Co-Authors: Usman Khalid Awan, Bernhard Tischbein, Christopher MartiusAbstract:Accurate quantification of the rate of ground- water (GW) recharge, a pre-requisite for the sustainable management of GW resources, needs to capture complex processes, such as the upward flow of water under shallow GW conditions, which are often disregarded when esti- mating recharge at a larger scale. This paper provides (1) a method to determine GW recharge at the field level, (2) a consequent procedure for up-scaling these findings from field to Irrigation scheme level and (3) an assessment of the impacts of improved Irrigation Efficiency on the rate of GW recharge. The study is based on field data from the 2007 growing season in a Water Users Association (WUA Sho- makhulum) in Khorezm district of Uzbekistan, Central Asia, an arid region that is characterized by a predominance of cotton, wheat and rice under Irrigation. Previous quali- tative studies in the region reported Irrigation water supplies far above the crop water requirements, which cause GW recharge. A field water balance model was adapted to the local Irrigation scheme; recharge was considered to be a fraction of the Irrigation water losses, determined as the difference between net and gross Irrigation requirements. Capillary rise contribution from shallow GW levels was determined with the HYDRUS-1D model. Six hydrological response units (HRUs) were created based on GW levels and soil texture using GIS and remote sensing techniques. Recharge calculated at the field level was up-scaled first to these HRUs and then to the whole WUA. To quantify the impact of improved Irrigation Efficiency on recharge rates, four improved Irrigation Efficiency scenarios were devel- oped. The area under cotton had the second highest recharge (895 mm) in the peak Irrigation period, after rice with 2,514 mm. But with a low area share of rice in the WUA of \1 %, rice impacted the total recharge only marginally. Due to the higher recharge rates of cotton, which is grown on about 40 % of the cropped area, HRUs with a higher share of cotton showed higher recharge (9.6 mm day -1 during August) than those with a lower share of cotton (4.4 mm day -1 ). The high recharge rates in the cotton fields were caused by its water requirements and the special treatment given to this crop by water management planners due to its strategic importance in the country. The scenario simulations showed that seasonal recharge under improved Irrigation Efficiency could potentially be reduced from 4 mm day -1 (business-as-usual scenario) to 1.4 mm day -1 (scenario with maximum achievable Efficiency). The com- bination of field-level modeling/monitoring and GIS approaches improved recharge estimates because spatial variability was accounted for, which can assist water managers to assess the impact of improved Irrigation effi- ciencies on groundwater recharge. This impact assessment enables managers to identify options for a recharge policy, which is an important component of integrated management of surface and groundwater resources.
Usman Khalid Awan - One of the best experts on this subject based on the ideXlab platform.
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a gis based approach for up scaling capillary rise from field to system level under soil crop groundwater mix
Irrigation Science, 2014Co-Authors: Usman Khalid Awan, Bernhard Tischbein, Christopher MartiusAbstract:Capillary rise represents an often neglected fraction of the water budget that contributes to crop water demand in situations of shallow groundwater levels. Such a situation is typical in irrigated areas of Central Asia where water from capillary rise is exploited by farmers to meet production targets in Uzbekistan under uncertain water supply. This leads to higher water inputs than needed and creates a vicious cycle of salinization that ultimately degrades the agricultural land. In this study, capillary rise is quantified at different spatial scales in the Shomakhulum Water Users Association (WUA), situated in the southwest of Khorezm, Uzbekistan. The mathematical model HYDRUS-1D was used to compute the capillary rise at field level for three major crops (cotton, wheat and vegetables) on six different hydrological response units (HRUs). These six HRUs having homogenous groundwater levels (1–2 m beneath the soil surface) and soil texture were created using GIS and remote-sensing techniques. Capillary rise from these HRU was then up-scaled to WUA level using a simple aggregation approach. The groundwater levels simulated by FEFLOW-3D model for these HRUs in a parallel study under four improved Irrigation Efficiency scenarios (S-A: current Irrigation Efficiency or business-as-usual, S-B: improved conveyance Efficiency, S-C: increased application Efficiency and S-D: improved conveyance and application Efficiency) were then introduced into HYDRUS-1D to quantify the impact of improved efficiencies on the capillary rise contribution. Results show that the HRUs with shallow groundwater-silt loam (S-SL), medium groundwater-silt loam (M-SL) and deep groundwater-silty clay loam (D-SCL) have capillary rise contribution of 28, 23 and 16 % of the cotton water requirements, 12, 5 and 0 % of the vegetable water requirements and 9, 6 and 0 % for the wheat water requirements, respectively. Results of the scenarios for the whole WUA show that the maximum capillary rise contribution (19 %) to the average of all crops in the WUA was for the S-A scenario, which reduced to 17, 11 and 9 % for S-B, S-C and S-D, respectively. Therefore, it is recommended that before any surface water intervention or drainage re-design, water managers should be informed about the impacts on groundwater hydrology and hence should adopt appropriate strategies.
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combining hydrological modeling and gis approaches to determine the spatial distribution of groundwater recharge in an arid Irrigation scheme
Irrigation Science, 2013Co-Authors: Usman Khalid Awan, Bernhard Tischbein, Christopher MartiusAbstract:Accurate quantification of the rate of ground- water (GW) recharge, a pre-requisite for the sustainable management of GW resources, needs to capture complex processes, such as the upward flow of water under shallow GW conditions, which are often disregarded when esti- mating recharge at a larger scale. This paper provides (1) a method to determine GW recharge at the field level, (2) a consequent procedure for up-scaling these findings from field to Irrigation scheme level and (3) an assessment of the impacts of improved Irrigation Efficiency on the rate of GW recharge. The study is based on field data from the 2007 growing season in a Water Users Association (WUA Sho- makhulum) in Khorezm district of Uzbekistan, Central Asia, an arid region that is characterized by a predominance of cotton, wheat and rice under Irrigation. Previous quali- tative studies in the region reported Irrigation water supplies far above the crop water requirements, which cause GW recharge. A field water balance model was adapted to the local Irrigation scheme; recharge was considered to be a fraction of the Irrigation water losses, determined as the difference between net and gross Irrigation requirements. Capillary rise contribution from shallow GW levels was determined with the HYDRUS-1D model. Six hydrological response units (HRUs) were created based on GW levels and soil texture using GIS and remote sensing techniques. Recharge calculated at the field level was up-scaled first to these HRUs and then to the whole WUA. To quantify the impact of improved Irrigation Efficiency on recharge rates, four improved Irrigation Efficiency scenarios were devel- oped. The area under cotton had the second highest recharge (895 mm) in the peak Irrigation period, after rice with 2,514 mm. But with a low area share of rice in the WUA of \1 %, rice impacted the total recharge only marginally. Due to the higher recharge rates of cotton, which is grown on about 40 % of the cropped area, HRUs with a higher share of cotton showed higher recharge (9.6 mm day -1 during August) than those with a lower share of cotton (4.4 mm day -1 ). The high recharge rates in the cotton fields were caused by its water requirements and the special treatment given to this crop by water management planners due to its strategic importance in the country. The scenario simulations showed that seasonal recharge under improved Irrigation Efficiency could potentially be reduced from 4 mm day -1 (business-as-usual scenario) to 1.4 mm day -1 (scenario with maximum achievable Efficiency). The com- bination of field-level modeling/monitoring and GIS approaches improved recharge estimates because spatial variability was accounted for, which can assist water managers to assess the impact of improved Irrigation effi- ciencies on groundwater recharge. This impact assessment enables managers to identify options for a recharge policy, which is an important component of integrated management of surface and groundwater resources.
