فهرست مطالب سروش برخورداری

This study determined the surface and groundwater resources portions aimed at identifying the contribution of water resources in an irrigation district by simulating the process of surface water distribution in irrigation canals, spatial analysis of water distribution. The Abshar irrigation district located in Isfahan city was selected as a case of this study. The simulation of water distribution within the canals was performed by the development of an integral-delay simulator model in the MATLAB, and the spatial analysis of the water distribution adequacy index was performed in the GIS. The water requirement of the crop pattern products was also estimated using the NETWAT program. The main and sub-canals' simulation results indicate a frequently decreasing of water delivery adequacy from upstream to downstream units, especially under the water shortage scenarios, indicating the poor efficient management of water distribution in the canal district. The spatial analysis of irrigation water distribution adequately indicated the inefficiency of surface water delivery and the main reason for the increase in the number of wells drilled by farmers within the irrigation district. Subsequently, by determining the amount of surface water portion in the second and tertiary agricultural area and analyzing the operation information of wells located in the irrigation district, the tables of the contribution of surface and groundwater resources were performed separately for the secondary and tertiary irrigated units. The results of this study provide the basis for implementing the water accounting system, with the portion of surface and groundwater resources within the irrigation district.

By developing a hydraulic simulator model of flow in irrigation canals, this study proceeded to spatially evaluate the adequacy of irrigation water distribution in the main and secondary canals of the waterfall irrigation network located in Isfahan province. For this purpose, a water distribution simulation between main and secondary canal catchments was performed during an irrigation season, based on spatial analysis of the water distribution performance adequacy index. According to what is done, daily distribution and delivery planning based on the information of water supply, water sales, and specified share for each second and third-degree intake valve, and with a simplified integral-delay mathematical model in MATLAB environment was linked. Five exploitation scenarios, representing normal conditions, waterlogging, and water scarcity, were considered following the prevailing patterns of surface water allocation - based on information collected in the last ten years from the irrigation network operation office. The simulation results in the main and secondary canals indicate a frequently decreasing trend of water delivery adequacy from upstream to downstream catchments, so that the adequacy index under water deficit scenarios of five, 15 and 30 percent in the range of 41-69 percent, respectively, 95-29 percent and 65-19 percent. The required water has reservoirs located downstream of the main canals. In addition to the nature of upstream control of the operation, the justification for this phenomenon is the inefficiency of the traditional manual operation method and the insufficient flexibility of water level adjustment structures and reservoirs in the reliable distribution of irrigation water under water scarcity scenarios. With the decrease in inlet flow due to water shortage, the vulnerability of the water distribution process in the downstream catchments has increased, and the favorable water delivery conditions can be seen only in a limited number of catchments located at the beginning of the main and secondary canals.

Seepage losses are a significant portion of losses along the main earthen canals in irrigation networks. The correct estimation of these losses will greatly help improve water productivity in the irrigation network. Due to the high capability of numerical models such as SEEP/W to estimate seepage rates in the canals, this method has been used as one of the most widely used in various researches (Barkhordari et al., 2019; Mohammad Rezapour Tabari & Mazak Mari, 2016). Despite various investigations in this regard, the seepage rate was not evaluated for the presence of heterogeneous and non-isotropic conditions in the canal bed. Therefore, in the first step of this study, the Seepage rate in the earthen canal of Moghan irrigation network was evaluated using the SEEP/W model. In the second step, in order to further investigate and predict the possibility of changing the hydraulic properties of the soil in the long-term, a comprehensive assessment was carried out on the permeability coefficient.

After collecting field data and measurements based on the existing and governing conditions (hydraulic, geometrical data, and soil geotechnical) along the Moghan canal, and also based on changes in some of these parameters, the problem is defined in the SEEP/W model based on 7 reaches. In order to calibrate the model, evaluation of simulated values with measured values of seepage using the CRM statistical coefficient was considered. Then, in order to further investigate and predict the possibility of heterogeneous and non-isotropic conditions in the soil system, a separate seepage analysis was conducted in the Moghan canal by changing the values of kx and ky kx-1. To achieve this objective, a reasonable range of 5×10-8 to 8×10-7 m/s was determined for kx based on the canal bottom and side walls materials. The range of 0.1 to unity was selected for ky kx-1.

The results of the main simulated showed that the deviation of the simulated values by model seepage from the measured values (CRM) is less than 0.1. Considering the distribution of other parameters such as the hydraulic gradient and pore-water pressure, concluded that due to the higher hydraulic gradient in the canal bottom than its side walls (equal to 1.6 and 1.2 at reaches 1, 2 and 3, and also 1.4 and 1 at reaches 4, 5, 6 and 7, on the bottom and its junction with the side walls in the canal, respectively), the water outlet potential is greater in this area. Therefore, the uniform lining of the bottom and side walls in water canal reaches can be considered as a successful solution that is based only on modelling results. Also, the maximum amount of pore-water pressure is at a distance of 3-4 times of the water depth in the canal, relative to the bottom of the canal and along the vertical profile of the soil. Further, the results of seepage analysis indicate that considering the severity of each of the long-term sedimentation and erosion conditions, it is possible to estimate a maximum seepage rate to 20838.6×103 L/day and a minimum to 245.4×103 L/day as an initial estimate, without the need for modelling in this canal, is predictable.

In this study, seepage rate in the earthen canal of Moghan irrigation network was evaluated using the SEEP/W model. The modelling results showed that the deviation of the simulated values by model seepage from the measured values (CRM) is less than 0.1. Then, in order to further investigate and predict the possibility of changing the hydraulic properties of the soil in the long-term, due to the possibility of heterogeneous and non-isotropic conditions in the soil system, a comprehensive assessment was carried out on the permeability coefficient. The results of this analysis indicate that considering the severity of each of the long-term sedimentation and erosion conditions, it is possible to estimate a maximum seepage rate to 20838.6×103 L/day and a minimum to 245.4×103 L/day as an initial estimate, without the need for modelling in this canal, is predictable. Also, the results of this model regarding the distribution of other parameters such as hydraulic gradient and pore-water pressure, showed that the maximum amount of hydraulic gradient was 1.4 to 1.6 in the bottom and also at the junction with the side walls of the canal. Also, the maximum amount of pore-water pressure is at a distance of 3-4 times of the water depth in the canal, relative to the bottom of the canal and along with the vertical profile of the soil.

Seepage losses and poor operational activities are the two main source of water losses throughout the agricultural water conveyance and distribution systems in irrigation districts. This study aims to investigate the performances of two strategies of “canal lining” and employing the “Canal Automation” in order to reduce the losses mentioned above. The investigation was carried out on a couple of main canal reaches of Moghan Irrigation Districts. Two numerical models were simulated by Seep/w software to compare the seepage rate between the canal with and without concrete lining. The results reveal that the ability of concrete lining to reduce seepage losses along the canal is about 10%. Performance assessment of the “Canal Automation” strategy to minimize operational losses within the main canal was carried out employing Model Predictive Control (MPC). The results of the latter strategy indicate that employing the MPC not only reduces the operational losses along the canal by 15% but also improves the operation of the main canal so that the minimum efficiency and adequacy performance indicator was obtained 100% and 83% respectively. Therefore; due to Executive considerations and financial constraints in the same cases, the potential of each of the two strategies can be considered to reduce the conveyance and distribution losses and ultimately choose the most suitable option.