فهرست مطالب شکرالله آبسالان

The role of water in agricultural development and economic growth is undeniable. The imbalance between water supply and demand in Iran has created a challenge for the management of water resources, especially in agriculture. Paying serious attention to water productivity and improving it through appropriate methods and policies is one of the most effective solutions to address the water crisis and enhance the quantity and quality of agricultural production. The concept of water productivity is to produce the best and most products with the least amount of water. Agricultural water productivity has received serious attention in recent years from scientific societies related to irrigation and agriculture. The variation in water productivity for different crops at the local level and in comparison with other countries with similar climatic conditions indicates the potential for increasing agricultural water productivity. In the present research, the productivity of agricultural and horticultural products was investigated through field surveys, field measurements, and remote sensing analyses.

First, the status of water resources in the aquifer, including changes in groundwater levels and programmable water, was investigated. Then, the water consumption of agricultural plants was calculated using the difference between effective rainfall and plant water requirement (evaporation-transpiration). In the next step, the cultivated area of Basht Aquifer was examined using Sentinel-2 satellite images in Google Earth Engine software. Yield, dates of planting and harvesting, and irrigation times for agricultural products were verified through questionnaires completed by farmers and experts. After that, the water requirement of the current cultivation pattern was calculated using the FAO Penman-Monteith method. Finally, the productivity of different products was determined by evaluating the products in terms of productivity.

The area of the alluvial aquifer was 45.5 km², with an average length of about 25 km and a width of 5 km. The total volume of discharge and extraction from groundwater resources was 39.723 MCM. The infiltration amount of the Basht alluvial aquifer was calculated to be 7.905 MCM. By joining the outflow streams, including transfer streams through different elevations, the aquifer was recharged with a total of 20.377 MCM. Calculations using the FAO Penman-Monteith method showed that the water requirements of the dominant crops in the aquifer, including citrus fruits, wheat, barley, corn, canola, watermelon, rice, legumes, and alfalfa, were 9170, 5630, 4821, 7863, 5411, 9291, 20234, 5225, and 14083 m³, respectively. In total, the amount of water consumed by the agricultural products of Basht Aquifer was nearly 45 MCM, which was approximately equivalent to 1 m³m⁻² of the cultivated area. This is 2.64 times higher than the amount of water that can be programmed for agriculture (17 MCM).

The cultivation pattern will be influenced by parameters such as the climatic compatibility of products, the potentials of water and soil resources, regional needs, customs and interests of local people, and economic evaluation and income from production. Any change in the cultivation pattern should consider all social, economic, and environmental factors. However, given the existing conditions of the water sources, any cultivation pattern (even those considering high income) that increases discharge compared to the aquifer's recharge sources will be dangerous for future sustainability and will cause groundwater salinization and aquifer subsidence. Cultivation of high water-consumption plants such as seed corn should be stopped due to the severe water conditions of the region, and more investment should be made in developing crops such as canola, which are better adapted to the region's climate.

This study was conducted to compare and monitor drip and surface irrigation systems for corn and wheat crops in three planting seasons from summer 2016 to spring 2018 in one of the agricultural research stations in Khuzestan, located in Ahvaz. The source of irrigation water was Karun River with salinity of 3 dS/m in Ahvaz section. This study was performed using randomized complete blocks design with three replications. The basis of blocking in corn cultivation was 2 and 4 days irrigation intervals, and in wheat cultivation, the distances between drip lines were 40, 60, and 75 cm. The results showed that the volume of water used in the drip system for corn and wheat was 24% and 32% lower than the surface irrigation system, respectively. Also, water productivity in the drip system was higher than surface irrigation system by 16% and 21%, for corn forage and grain, respectively, and by 35% for wheat. Wheat water productivity for different distances of drip lines was not significantly different. Therefore, in heavy-textured soils, drip irrigation lines at 75 cm spacing can be used for wheat cultivation. In soil monitoring analysis, the drip system reduced soil quality such that, after three planting seasons, the initial non-saline-sodic soil (ECe = 3.09dS / m, ESP = 6.18%) became saline (ECe = 7.63dS / m, ESP = 12.63%). Despite accumulation of salts at the periphery of the wetted soil under the drippers, the plants had a better growth and yield in the drip system than the surface irrigation, because of the high soil water potential around the roots and under the drippers, which reduced salt effects. The results of this study showed that if a drip system is used for the climate similar to the central and southern regions of Khuzestan, land drainage and leaching operations at the end of the growing season are necessary to protect the soil.

In order to optimize the efficiency of water in agriculture, it is necessary to know the extent of water leakage in the lined canals. In this study, water conveyance efficiency and seepage/leakage losses were determined to evaluate earth and concrete lined channels in Khuzestan irrigation networks. The result of this assessment was to identify the problems of management and damages in these channels. Thirty channels were studied and evaluated in the main irrigation and drainage networks of Khuzestan province, including Karun, North Khuzestan, Karkheh, Shavour and, Zohreh and Jarrahi, and channels managed by the farmers. There were 17 tertiary and quaternary canals and 6 earth channels in irrigation networks, as well as 1 canal and 6 earth channels under farmers’ management. The water conveyance efficiency in canals ranged from 38.9% in Ramshir to 99.7% in Shushtar; and in the earth channels, from 46.9% in Baghmalek to 89.3% in Shush. The comparison of means of the measured and calculated indices was performed by t-test and showed that seepage per km length of the unlined earth canals was 3017.7 m3/day, which had no statistically significant difference with lined canals with a leakage of 2166.2 m3/day/km. The results of Pearson correlation coefficients showed that there was a negative and significant (at p<1%) correlation between distribution efficiency with the amount of seepage per kilometer channel length, and between losses and the input flow rate per km of channel length. Also, 16.7% of the total canals had a water distribution efficiency of less than 67.8% (between 38.9% and 67.8%), while 50% of the canals had a conveyance efficiency of less than 68.6%. The low water losses in half of the concrete lined canals and the excessive water loss in 11% of such canals, which even increased water losses in the earth's channels, reveals the necessity of paying attention to the optimal management of these canals. This optimal management should be considered at the design and construction stages of the structure as well as during the installation in agricultural lands. Attention should also be paid to use of proper seals and other suitable equipment to prevent water leakage.

Management of irrigation networks can play a very important role in the hardware and software performance of these networks. In this research, by conducting field studies on suspended sediment transport and conveyance efficiency, the effect of operating conditions on sedimentation and water losses at Khouzestan province irrigation networks was analyzed. The inflow-outflow method and sediment flux continuity equation were used to determine the canal losses and sedimentation of suspended load in the studied reaches, respectively. The investigation was done on 4, 21 and 16 reaches of the main, secondary and tertiary channels, respectively. The ratio of free board of flow in canal as operation index was computed. The effects of this index on sedimentation rate and water losses relative to input discharge were studied in each kilometer of the canal. Results showed that 10% decreasing in the operational discharge relative to the designed discharge caused 0.23 and 0.26 kg s-1 km-1 increasing in sedimentation rates of the main and secondary channels, respectively. As the distance from the upstream of the main channel increased, the channel efficiency decreased. So that the increasing rate of the water losses in main channel of Karkheh irrigation network was 0.12 percent of the entrance discharge in each kilometer distance from the beginning of the channel. The increasing rate of water losses for the western and eastern channel of Dez irrigation network were 0.16% and 0.09%, respectively.

Water scarcity is a major constraint in the development of rice farming in some parts of the world. In many areas, the volume of water consumed in the field and during the growing season of rice is usually more than the actual requirement due to traditional flood irrigation. In the province of Khuzestan, irrigation water requirement is potentially high due to the coincidence of rice cultivation with the beginning of hot months of the year. In traditional irrigation management, regular water entry and exit from the basins is commonly used to reduce water temperature and create a cool environment for plant development. This system causes a lot of water losses. It seems that a change in the irrigation method of rice fields is necessary. The application of new technologies, such as pressurized irrigation systems, can be an appropriate approach to reduce future problems related to increasing water shortages. In this regard, the study of pressurized irrigation systems has been considered as one of the strategies for reducing water consumption and increasing water productivity in rice cultivation in the research program. Result of a research in Pakistan about water use efficiency and economic feasibility of growing rice with sprinkler irrigation showed that the application of this system increased the yield of rice by 18%, while the water consumed was 35% less than the traditional irrigation system (McCauley, 1990).

Azadegan Plain (AP) in Khuzestan province is located in the downstream of Karkheh River Basin (KRB). Wheat is the main crop cultivated in this plain and beacause of soil and water limitations¡ mainly salinity and waterlogging¡ its average yield is not beyond 1.5 tons per hectare. The objective of this research is to find out the limitations and sources of inefficiencies in enhancing water use efficiency (WUE) of Wheat crop in the AP. Hence¡ based on information and data obtained from the the two years experiments¡ some extention approaches and measures were proposed for the improvement of Wheat’ WUE in the plain. Analysis of measured WUEs indicated that the range of variation in WUE values is relatively high and varies between 0.1-2.1 Kg.m-3. Evaluation of results indicated that sources of inefficiencies and the limiting factors affecting WUE in the AP are combined effects of soil salinity¡ waterlogging¡ poor irrigation management¡ and other crop and field management practices. For obtaining higher WUEs in the plain¡ the following actions should be practiced: 1) The common traditional irrigation method to be changed the basin irrigation method¡ 2) The proper plots to be conducted based on the field slope¡ 3) Construction of fixed and simple water barriers for water intake to the field channels¡ 4) Ttraining of the farmers and required technical support to them.

This study aims to evaluate the present management of border irrigation systems applied to wheat, alfalfa and sugar-beet farms in Boyer-Ahmad and Gachsaran cities in Kohgiloyeh and Boyer-Ahmad Province. Experimental farms included 8 alfalfa farms, 5 wheat farms and 5 sugar-beet farms. The experiments were conducted at different growth stages of plants and customary borders with prevalent dimensions, slopes, and management practices. The relationship between management allowable deficit, moisture deficit before irrigation, and infiltrated depth indicated that in most cases either “deficit irrigation” or “stress irrigation” had been applied. This type of irrigation has positive effects on water use but negative effects on supply of required soil moisture for plants. In the first to third irrigations, measured application efficiencies ranged from 40.8% to 100%, 52.2% to 100%, and 61.1% to 100%, respectively. Graphs of advance, recession, and ideal recession showed the effects of border slope and length on inflow cut time and uniformity of water distribution. Water infiltration curves showed the amount of deficit irrigation. The results showed that weak irrigation management is the result of three parameters: lack of knowledge on the part of farmers about soil moisture conditions and correct time for irrigation, weak irrigation scheduling, as well as an imbalance between available water supply and irrigation requirements which leads to wasting water and reduced irrigation efficiency.