مجله آبیاری و زهکشی ایران
سال ششم شماره 3 (پاییز 1391)

This research work was aimed to investigate agricultural water demand and water requirement using HadCM3 model that occur due to climate change in Aidoghmoush irrigation network at time period 2026-2039. At first، monthly temperature and precipitation data of HadCM3 model were provided and downscaled in the baseline period (1987-2000) and the future period (2026-2039) under the SRES emission scenario، namely A2. Results showed that the temperature increased (Between 1. 0 to 1. 8) and precipitation varied (-28 to 33 percent) in 2026-2039 compared with baseline period (1987-2000). In order to estimate the water requirements، crop evapotranspiration and effective rainfall were calculated. The potential evapotranspiration and the crop evapotranspiration were calculated to FAO Penman-Monteith and FAO-24 method، respectively. Calculation the potential evapotranspiration in future periods (due to lack of information) through the relationship of temperature and potential evapotranspiration in the base period was conducted. Then، for risk analysis، downscaled temperature and precipitation for 2026-2039 were introduced to water requirement model and monthly net water requirement was simulated in the future and in the sequel، water demand and the risk increase of its changing considered. The study also revealed risk increase in agriculture water demand، as these increase is of 10 to 13 (for the risk of 50% and 25%). Considering the present areas of the selected crops (wheat، barley، alfalfa، soya، feed corn، forage maize، potato and walnut) and their augmented requirements، volume of 6 to 9 MCM/y for 2026-2039 period (for the probability of 50% and 25%) will be required to meet the demands. Finally، it is found that responses of the crops were different where wheat and barley more variability to this phenomenon.

The use of unconventional water sources (e. g. wastewater treatment plants effluent) as well as the use of high efficient irrigation systems (e. g. drip irrigation systems) has found special merit in today''s water resource management in agriculture. Drip irrigation systems، however، can lead to operational problems such as clogging، precipitation and corrosion of pipes and emitters، especially when effluent from wastewater treatment plants is used as the main source of irrigation. Such problems can shorten the irrigation system life cycle and increase the maintenance costs، significantly. In this research، the quality of effluents from the city of Mashhad Wastewater Treatment Plants (Olang، Parkand Abad 1، and Parkand Abad 2) were evaluated in order to assess the feasibility of using drip irrigation systems. For this purpose، the main parameters of importance in clogging and corrosion of drip irrigation systems such as pH، total dissolved solids، total suspended solids، Iron، Manganese and total coliform bacteria contents of the effluents were measured regularly over a period of one year. The results of the study indicated that the use of drip irrigation system is strongly limited due to the high concentration of bacteria in the effluents (4. 8-7. 3 log CFU/100 mL)، which can initiate clogging of pipes and emitters. In regard to other effluent quality parameters including pH (7. 3-8)، TDS (800-1200 mg/L)، TSS (42-138 mg/L)، Iron (0. 2-0. 6 mg/L)، Manganese (0. 1-0. 4 mg/L) and langelier saturation index (LSI) (-0. 7-0. 6)، application of drip irrigation systems also encountered limitations in the range of low to moderate levels. In summary، in order to reduce the operational problems associated with drip irrigation systems، the use of advanced methods for further treatment of the effluents such as filtration، membrane treatment، and the use of appropriate chemicals are recommended.

Sustainable development of pressurized irrigation systems is a key to mitigate the crises of water scarcity، mainly because of more demand for food، in Iran. However، despite the importance of the issue، little areas of lands are equipped with the pressurized irrigation systems and still there are long way to reach to the desired level. Moreover to the different technical، technological، and infrastructure problems and challenges associated with the sustainable development of pressurized irrigation systems in Iran، socio-economic and policy –institution issues and problems are among the important cases. Therefore، the objective of this research project was to systematically identify the socio-economic and policy–institution problems، issues، and challenges associated with the sustainable development of pressurized irrigation systems in Iran. The methodology of the program was fully participatory، with the participation of representatives of different stakeholders in the water and the agriculture in general، and the experts، and resource persons in pressurized irrigation enterprise of the country in specific. The ISNAR approach was used here. The experts were gathered and participated in the different brain storming meetings to identify the relevant problems، issues، and the challenges. The research outputs were mainly in the form of problem trees. However the identified problems were also prioritized، based on their importance، and some related strategic pivots were also developed finally. Based on the results، the main socio-economic and policy –institution problems hindering sustainable development of pressurized irrigation systems in Iran could be categorized in the following categories: Economic and finance problems (including national economy، costs to the beneficiaries، banking and finance and credit issues)، socio-cultural problems (including socio-cultural basis and capacity building، inefficiencies in adoption of the systems، and weaknesses in agricultural production systems)، policy and institutions issues (including organizational and human resource structures weaknesses، and problems associated with the policy and planning، inefficiencies in motivation of beneficiaries willingness toward the acceptance and adoption of the systems). Quantity basis، the economic-finance، socio-cultural، and policy-institution problems were totally 88 cases، and based technical discussions and comments of the stakeholders assigned into different selected categories. From the strategic aspects، results of this research indicated that the following strategies should be implemented in the country for the sustainable development of pressurized irrigation from socio-economic and policy institutions aspects: 1) More involvement of the private sector in pressurized irrigation systems development and hence disengagement from the government 2) More attention to energy savings in the systems، considering growing demand of energy and energy prices increase to happen in near future 3) Selection of economic criteria in prioritizing development of pressurized irrigation systems in different regions، and 4) More focus of research studies and plans on measures for economic justification of using pressurized irrigation systems in small farms.

The Karkheh River Basin (KRB) is suffering from low rainfed agricultural productivity and supplemental irrigation (SI) is recommended to increase agricultural water productivity and suitable livelihood of stakeholders. Supplemental irrigation (SI) potentials of the basin are determined and impact of SI developing to the Karkheh Dam are studied. Suitable areas for SI in 53 subbasin with intersecting layers in GIS framework are prepared.. SI water requirement for early sowing (100 mm in autumn) and two levels of deficit SI strategies in spring (total 150 mm) are considered. Exceedence probability 80% of river discharge was considered as hydrological drought and 15% of mean annual runoff are assumed as minimum value of environmental flow in each subbasin. A Fortran program was developed to dynamically allocate the stream flow to the areas suitable for SI. For water allocation، four scenarios of normal flow condition، drought condition with environmental flow consideration for each one are considered. Results indicate that under normal flow conditions (30-year mean average flow)، and under drought conditions the area that could be irrigated ranged between 1945 and 975 km2 and in normal seasons could decrease downstream flow by 15%، whereas in drought condition، that would be up to 10% of current flow، if all potential suitable areas for SI are developed. It is recommended that spring SI be emphasized under the KRB water availability conditions.

Realizing the full potential of drip irrigation technology requires optimizing the available parameters، such as the frequency، rate، and duration of water application. Numerical simulation is a fast and inexpensive approach to studying optimal management practices. Unfortunately، little work has been done to investigate the accuracy of numerical simulations. The purpose of this research is the comparison of HYDRUS-2D simulations of drip irrigation with experimental data. In this study، a sandy-loam soil was irrigated using T-Tape drip tubing. Three various drip irrigation trials (30، 45 and 75 hr) were carried out. At the end of each irrigation، the condition of water distribution in the soil was determined by gravimetric sampling. The results showed that HYDRUS-2D has high ability in prediction of soil water content distribution and can use as a useful tool for investigating and designing drip irrigation management practices. Also، various methods of ROSETTA were evaluated for hydraulic parameters estimation and results showed that complete model can provide reasonable results.

Considering different bases in design، operation and implementation of pressurised irrigation networks، compared to open channel networks، development of specific performance evaluation model for these networks is necessary. Because of dependence of main and farm systems، performance evaluation of the whole network، requires that both main and farm systems to be evaluated simultaneously، which is not considered in previous models. In this research NPAPIS model is developed with capability of evaluating management، technical، economical، environmental and social perspectives. For each perspective، several appropriate sub-perspectives for both main and farm systems are defined. This model used the key indicators to calculate the performance score for perspectives، sub- perspectives، and the entire network. The performance evaluation is done in rapid and comprehensive fashion، and the performance validity is calculated. For presentation of NPAPIS model application، Akramabad unit of Aydoghmoush irrigation network was chosen. The results indicate that the best mark for performance belongs to the management perspective with performance grade of 77. 3%، with the validity of 95. 5%، the worst mark belongs to economical perspective with the performance grade of 24% and validity of 51. 1%. The successful application of NPAPIS model for performance assessment of Aydoghmoush irrigation network، recommends that this model to be used as an appropriate tool for performance assessment of other pressurised irrigation networks.

Measured flood hydrograph of Zangmar Ephemeral River between Makoo and Poldasht hydrometry showed that the volume of exit hydrograph from Poldasht station is significantly less than input hydrograph in Makoo station. While there are not any lateral outflow from the river reach with 62 km length and the amount of evaporation and direct remove during flood occurring is very little. These transmission losses can be caused by water infiltration from the river’s bed and flood plains. Due to transmission losses and lack of initial flow flood routing in these rivers is impossible with conventional methods and it is necessary to develop methods of flood routing. Therefore in this study a computer model for natural river cross section has been developed in which partial differential equations of unsteady none uniform flow (Saint-Venant equations) is linearization by finite difference method. To calculate seepage losses Muskat’s equation integrated with Saint-Venant equations. The equations have been developed in such a way that seepage losses can be calculated simultaneously. The results showed that with considering seepage losses، the developed model can predict the output hydrograph in comparison with field data with good accuracy. The results of flood routing for 13 input hydrograph showed seepage losses in the river reach is an average of about 74% of the input hydrograph volume.

Mid-season and end-season drainage are two major water management practices in paddy fields so that، the former increases crop yield and the latter provides more suitable conditions for rice harvest. In this research، the implementation effect of these management practices through surface and subsurface drainage systems on phosphorus losses was evaluated at the 4. 5 ha consolidated paddy field of Sari Agricultural Sciences and Natural Resources University، at summer of 1390. Drainage treatments were: three conventional subsurface drainage systems including drainage system with drain depth of 0. 9 m and drain spacing of 30 m (D0. 9L30)، drain depth of 0. 65 m and drain spacing of 30 m (D0. 65L30)، and drain depth of 0. 65 m and drain spacing of 15 m (D0. 65L15); a bi-level subsurface drainagesystem with drain spacing of 15 m and drain depths of 0. 65 and 0. 9 m as alternate depths (Bilevel)، and surface drainage system (Control). Tarom rice cultivar was planted on Tir، 30 and was harvested on Mehr، 18. During rice growing season، the various components of total phosphorus (TP) balance were measured in drainage treatments. The value of TP input to all treatments was 29. 4 kg. ha-1، of which 0. 007، 0. 02، 0. 007، 0. 003، and 0. 147 kg. ha-1 was lost through mid-season and end season drainage in Bilevel، D0. 65L15، D0. 65L30، D0. 9L30، and Control treatments، respectively. The minimum and maximum of total drainage and leaching losses of TP were 0. 204 and 0. 427 kg ha-1 which were occurred in the Bilevel and control treatments، respectively. Based on the results، performing mid-season and end-season drainage through subsurface drainage systems had less environmental impacts on water resources from phosphorus release point of view، compared with surface drainage.

The agricultural water price plays a key role in the optimal allocation of water resources، financial independence of irrigation networks، water costs supply and increase water productivity. The main aim of the present study is to develop a multi-criteria fuzzy model for water pricing in irrigation networks. The model was used for analyzing water price of Varamin irrigation command area. For this purpose، thirteen effective criteria on water price of irrigation schemes were considered. The most important steps of the development process included determination of the criteria’s values and normalizing them، computing weight of the criteria، definition of classes and classification، forming membership vector، forming price vector، and combination of the vectors. The results showed that the criterion of irrigation network type، independence of public support، and income per unit of area had the greatest impact on water price. The proposed model estimated the water price of the study area 547. 33 Rls/m3، as well the water price obtained 944. 33 Rls/m3 based on water harvesting cost approach. The findings indicated that the current water price of command area (96 Rls/m3) has a large difference in compare to the developed model and water harvesting cost approach. It is emphasized that there is a major distance between the real water value and the current water price. The multi-criteria fuzzy model with considering the actual conditions of irrigation district، in which almost all criteria have a value less than the ideal value، can accurately estimate the agricultural water price. The water price obtained with the proposed model may be utilized as the real water price of irrigation network، but the requirement frameworks have t be prepared. The proposed model has a desirable accuracy for assessing the effective parameters of water price in irrigation networks and can be utilized to determine the water price of these systems.

To study the effect of 3 depth of placement of drip irrigation tape on yield and quality of potato (cultivar Agria)، an experiment was conducted in a randomized complete block design، in Fariman region (2010- 2011). Treatments was include، 0، 10 and 20 centimeter، installation depth of drip irrigation tape. The results showed that the yield of potato strips installed on the soil surface were more than installed at depths of 10 and 20 cm and had significant difference at 5% level. But there were not significant differences between the strips that installed at 10 and 20 cm depth. The effect of tape drip irrigation installation depth on the marketability tubers was not significant، but the number of marketability tubers was reduced from 0 to 2 and 3 depth respectively. The effect of depth of drip irrigation tape installed on the mean tubers weight was not significant. The water use efficiency of surface Tape drip irrigation had significant different with subsurface drip irrigation treatments and was more than them. Generally، surface drip tape irrigation was better than subsurface drip tape irrigation.