Iranian Journal of Irrigation and Drainage
Year:2011 | Volume:4 | Issue:3|Papers Count:20

Estimating reference evapotranspiration (ETo) is essential in studies related to water resource management. The FAO56-Penman-Monteith combination method (FAO56-PM) is recommended as a standard method for estimating ETo. Since FAO56-PM method needs many input variables, ETo can be estimated by empirical methods that need fewer input variables. In this paper, performance of five radiation and temperature based methods for estimating daily ETo at nine stations in different climates were evaluated. Radiation based models ranked as the best method in humid climate, while in both arid-semiarid and extremely arid climates, temperature based models performance were better. Relative importance of meteorological variables influencing ETo was studied using multivariate statistical method of Factor Analysis. The minimum and maximum temperatures were most important variables in estimating ETo at all climates. Relative humidity and sunshine hours had also high effect on ETo at humid climate, while they had less effect on ETo at arid-semiarid and extremely arid climates. Effect of wind speed on ETo in the humid climate was negligible, while it had relatively high effect on ETo at arid-semiarid and extremely arid climates.

Initial soil moisture has high effect on infiltration characteristics, but it has not received much attention in measurement. This study was conducted to evaluate the initial soil moisture on infiltration characteristics and sensitivity Analysis of Kostiakov, Philip, Horton, Modified Kostiokov and SCS infiltration models and to find out the best infiltration model for Nehmat Abad Agriculture Research Station soils in agriculture faculity of Tabriz Azad Islamic University. The infiltration tests were carried out with double rings and 9 various initial soil moistures. The results showed that accumulation infiltration and time to reach the final infiltration reduces by increasing of initial soil moisture. Also Kostiokov and Philip methods were found the most suitable and SCS method unsuitable for the soils of the region. The coefficient of b in Kostiokov and Modified Kostiokov models and S in Philip had low sensitivity to initial soil moisture but coefficients of C and A in Modified Kostiokov and Horton models showed high sensitivity. Finally, results showed that Philip model had least and Modified Kostiokov model had the highest sensitivity to initial soil moisture variability.

Kor River is one of the important water resources of Fars province in southern part of Iran. Many big industrial, agricultural and residential departments are near this river. Therefore, implement of integrated researches about its pollution and using management tools such as mathematical models for simulation of water quality of this river and prediction of water quality or future are necessary. In this research quality of Kor River after Doroodzan dam up to Tashk and Bakhtegan lakes was determine according to the measured data Qual2k model was calibrated and then water quality of this river was simulated. For determination of sampling stations and also pollution sources for Kor river, 12 sampling stations were determined from the below of Doroodzan dam up to Bakhtegan lake. For evaluation of QUAL2K model, some statistical parameters including d (index of agreement), RMSE (Root mean square error), and MAE (mean absolute error) were determined. According to this research, the prediction of low flow duration was better than high flow duration because runoff in low flow was lower than high flow. The runoff is nonpoint source pollution, therefore this model can not predict that with good accuracy. Most accuracy prediction was for Ammonia and then for Nitrate, EC, BOD, pH, orthophosphate and DO, respectively.

For the purpose of protection of canal bed against erosion and to prevent seepage from the bottom or side of a canal, different types of impermeable linings are used, which may face to several problems including damages due to uplift pressure while water table is high. Thus, it is necessary to provide a drainage system under hard lining of the canal to release the water pressure especially at the end of operation season, when canal is empty. The drainage system is included a layer of drainage material (made of aggregate or geosynthetics) and outlet.In this paper the assessment of geocompsite application as layer of drainage in the bottom and side of the canal is considered. The conclusion from the laboratory investigation and numerical model results (SEEP/3D), it is concluded that synthetic drain- filter (included two layer of geotextile and a layer of geonet in the middle) can be appropriate replacing for grain drain- filter, if technical characteristic for chose and design drain- filter to be noticed. Also, the placing drain –filter in side of the canal has no effect in increasing drainage system efficiency so it is not necessary to use of drain-filter in side of the canals. In additional the application of numerical model based on finite element for assessment, chose thickness and installation position of this material as drain – filter is recommendation.

Groundwater resources are very important for agriculture. In this study the spatial variability of groundwater salinity for two years (2002 and 2007) and groundwater depth for four years (1987, 1997, 2002 and 2007) was investigated using geostatistical methods in Mazandaran province. The interpolation methods were ordinary kriging and cokriging, and inverse distance weighing with distance power of 1 to 4. The performance of the prediction methods was evaluated though cross-validation with comparison criteria of root mean square error (RMSE) and mean bias error (MBE). The statistical analysis showed that groundwater salinity and especially groundwater depth have a large variance and coefficient of variation. The average groundwater depth increased from 1987 to 2007 and the average groundwater salinity decreased from 2002 to 2007. The geostatistical analyses showed that the groundwater salinity and depth are highly spatially correlated. The spatial structure of groundwater salinity and depth follow an exponential and spherical model, respectively. The results of crossvalidation indicated that the best interpolator for salinity estimation is inverse distance weighing with distance power of 1. For estimating groundwater depth, inverse distance weighing with distance power 3 for 1987, ordinary kriging and cokriging with similar accuracy for 1997 and cokriging for 2002 and 2007 achieved the best results. The prediction map of groundwater salinity showed that the salinity was increased from west to east. Based on the map of groundwater depth, south and southeast regions have the highest depth of groundwater. In addition to estimation map, kriging methods were able to present the map of estimation variance for groundwater depth. These maps showed that the estimation uncertainty is smaller at sampling location and for nearby samples, and is larger as samples are more distant or where there is no samples. Therefore, when it is necessary to present the estimation uncertainty rather than estimation only, kriging should be preferred to inverse distance weighing.

Farm experiments are useful in knowing the drainage systems but they have considerable limitations including the inability to use them as prediction tools. Application of simulation models can cover these deficiencies but it is necessary to use the field data to evaluate the accuracy of the model. Two widely used drainage models are SWAP and DRAINMOD. The purpose of this research is to evaluate these models under filed conditions to simulate water table fluctuations and calculate optimum drain space and depth based on maximizing the crop production and minimizing drainage water. For this purpose, collected data from Mirza Kouchakkhan sugarcane farm in Khozestan in years 2001 and 2002 were used. The results showed that SWAP had better performance in calibration and verification periods. The RMSE for SWAP in calibration and verification periods were 15.18 and 14.85, respectively but they were 18.14 and 20.69 for DRAINMOD. Then, to find the best drain space and depth, for 28 different combinations of depth and space, crop production and drainage water were calculated. Considering the minimum crop production equal to 80 percent of the maximum crop production potential, for each model, 4 sets of depths and spaces were selected. Then, the set that had the minimum drainage water was selected as the best drain depth and space combination. This was 1.6 m depth and 25 m space for SWAP model and 1.15 m depth and 15 m space for DRAINMOD model. The difference can be attributed to the different crop production functions in two models. Because of limited data, in SWAP, a simple crop model was selected but in DRAINMOD, the effects of late plantation and over wet or dry conditions were taking into account and they changed the crop production.

Solute transport under saline conditions is of great interest. In this research, bromide transport in a saline soil's profile under three conjunction irrigation schemes using fresh and/or saline water was analyzed. Nine 0.7×2×1 m lysimeters filled with a saline clay soil from Segzi region of Esfahan province were used. Three conjunction strategy of fresh (1 dS m-1) and saline (14 dS m-1) water namely: blending, one-alternate and halfalternate were applied in a completely randomized design with three replicates. An equivalent of 30 g pure potassium bromide per m-2 was disssoloved in water and was uniformly applied onto top of each lysimeter followed by an 1.5 cm irrigation with fresh water. On eight sampling dates, following eight irrigation events, each lysimeter, s soil was sampled from seven depths. Results showed that, in most of the sampling dates, onealternate treatment caused more bromide leaching from soil surface layer (0- 10 cm) than the other two treatments. Therefore, one-alternate strategy may wash more salts from soil surface. Blending caused less bromide concentration in 0-25 cm depth. However, examination of the area under bromide profile revealed that the total remained bromide under blending treatment was lower than those under the other two treatments. Thus, blending of fresh and saline waters may cause greater leaching of bromide and probably greater leaching of other solutes past the lower boundary of soil profile.

World experience has shown that state management isn' t a good way to maintain and exploit water installations. The best substitutes are the organizations that can assure improvement of exploitation management and water distribution and maintenance in addition to decreasing the state role. To determine causes of farmers lack of tendency to participate in water user association, this study was conducted within the limits of drainage and irrigation network of the Miandoab plain during 2008-09. The necessary data and statistics were collected by conducting interviews and filling of 400 questionnaires. According to the results, more than 62% of farmers were not familiar with the goals of association and about 50- 60% of them were expressed no tendency to water user association or its partnerships' reflecting the lower convergence among the studied farmers. Also, based on the results Spearman correlation analysis, correlation between farmers' local responsibilities, their need for water users association, their knowledge about the aims of the water users association, their confidence to statements and activities of water affaires management and Zarrin-e-rood exploitation corporation, responsiveness among the farmers, their satisfaction of the drainage and irrigation network management and considering the role of extension and education with tendency of participating in water users association was significant.

Water crisis is main factor of agronomy limitation in all over the arid and semiarid area such as Hamedan. In these areas, water is not enough to meet crop water requirement during the growing period. Thus knowledge of sensitive irrigation timing is necessary for maximize yields and profits. A randomized complete block design on basis of split plot with four replications was applied to calculate the crop sensitivity factor and water stress effect in different growth stages of sugar beet. Experiment was carried out during the period of 2004-5 in Ekbatan station of agricultural and natural resources research center of Hamedan province. Growth stages were considered base on FAO growth periods and four irrigation treatments include %100, %85, %70 and %55 of irrigation water requirement were applied. Yield response factor on the basis root yield in first, second, third and fourth growth stage was 1.05, 0.82, 0.90 and 0.77 respectively. For sugar yield, this factor was 1.23, 1.02, 1.06, 0.84 and for total growth, stage for root and sugar was 0.88 and 1.03 respectively.

In order to study the effect of irrigation in different times on yield and irrigation water use efficiency in grape orchards, an experiment was conducted with randomized complete blocks design with 4 treatments and 4 replicates in Takestan Grape Research Station of Ghazvin, Iran in 2004-2005. Treatments included: (A) Control (furrow irrigation based on conventional irrigation in Takestan vineyards), (B) Furrow irrigation (on the base of phenological stages: inflorescence forming date, berry set, berry growth and verasion), (C) Furrow irrigation (20 days once after berry set) and (D) Furrow irrigation (30 days once after berry set) until grape ripening at Takestan region. The amount of water required in each irrigation on all treatments was based on water requirement of vineyards and the distance between two irrigation intervals as. The area of experimental plot was 120 m2. The results showed that B treatment increased yield and irrigation water use efficiency as compared to other treatments. In this treatment, the average yield was 16.05 ton/ha and irrigation water use efficiency was 3.3 kg/m3. Irrigation water use in B treatment compared with control treatment was reduced by 27.8%. The amount of water used in this treatment was less than other treatments. Therefore, timely irrigation and based on phenological stages in grape vineyards not only increased yield and irrigation water use efficiency but also decreased irrigation water consumption.

Investigation of current soil and water issues in arid and semi-arid regions is of great importance for sustainable soil water management. The existence of different solid compositions such as calcium carbonate in these soils, largely influence their hydraulic characteristics. These hydraulic properties have direct effect on maintaining soil water content. Direct measurement of soil hydraulic properties including retention curve and unsaturated hydraulic conductivity is expensive and time consuming. An alternative for direct measurement is then the use of indirect methods to predict the soil hydraulic functions. One promising indirect method in this regard is to derive the so-called pedo-transfer functions (PTFs). The objective of this study was to study the influence of soil calcium carbonate on water retention curve, using the derived PTFs. Consequently, 50 calcareous soil samples were randomly taken from Garmsar reagion, Iran. The soil article size distributions with and without calcium carbonate, bulk density and calcium carbonate contents were measured and used to derive the required PTFs at matric potentials of 0, 33, 50, 100, 300, 500 and 1500 KPa. The results indicated that the calcium carbonate content is the most important dominant parameter to predict the water retention curve for calcareous soils.

It is doubtful for experts to exactly assess the performance of irrigation and drainage networks, because of the uncertainty and vagueness of some operation and maintenance parameters. In this context, fuzzification of the weight and value of the criteria may improve the accuracy of assessment. The aim of this study is to develop a fuzzy analytical hierarchical model (FAHP model) for assessing Qazvin irrigation network and Foomanat, Markazi and Shargh irrigation networks of Sefidrood area. For that, 21 indicators in five groups of technical, management, environmental, economical and social are considered. Importance of each criterion is determined using FAHP with triangular membership function and based on experts decisions obtained from a questionnaire survey. The quantitative value of indicators is also calculated using field data. Results indicated that management criteria with aggregate weight of 0.350 and environmental criteria with aggregate weight of 0.113 have the maximum and minimum impact on performance of the irrigation systems, respectively. Hence, improvement of managerial factors status (operational services, degree of service on structures, adequate of requirement indicators operation and maintenance) is the most appropriate strategy for improving the performance of these systems. The performance value of Qazvin, Foomanat, Markazi and Shargh irrigation networks is determined 74.1, 65.4, 57.5, and 60.2%, respectively. Sensitivity analysis of the model demonstrates that any weight variation of the social criterion has a large impact on performance of the irrigation networks. The findings revealed that the FAHP model is an efficient approach to assess the performance of irrigation networks and may be applied as a management user-friendly tool of the assessment process.

Different types of sprinkler irrigation systems might be failed at design, performance and management stages and loses their desirable accomplishment. So, evaluation of sprinkler irrigation methods is practically not an avoidable necessity. Evaluation of sprinkler irrigation method means assessment of the irrigation efficiency, water distribution uniformity and water adequacy at a field. Certainly, high magnitude of each of the above parameters does not lonely shows a system performs well. This is because a comprehensive performance must have a high value of uniformity coefficient as well as a high magnitude of efficiency and prepare the maximum water requirement of the field. The objective of this research is the evaluation and the comparison of sprinkler irrigation systems including conventional solid set, wheel move and center pivot methods in Shahrekord Township. The Results show more suitable values of parameters such as, Christiansen uniformity coefficient, the low quarter uniformity and irrigation adequacy for conventional solid set system than the values of these parameters for wheel move and center pivot. Overall, under the soil, climate and system characteristics conditions in which the tests were carried out, the resultants show the parameters of evaluation have relatively acceptable values for sprinkler irrigation at Shahrekord Township.

Due to the importance of soil moisture in plants growth and biology interactions, it is considered as a key index of agricultural drought monitoring. In this research, to evaluate soil moisture deviation as an indicator of agricultural drought, a Soil Wetness Deficit Index (SWDI) was developed using satellite data of vegetation index (NDVI) and land surface temperature (LST). For this purposes, 8-day-products of land surface reflectance (MOD09Q1) and LST (MOD11A2) derived from MODIS satellite data over Esfahan in the period of 2000- 01 (dry year) and 2004-05 (wet year) 8-day time step were ordered and downloaded from internet. The SWDI in each time step was determined based on 8-day-Soil Wetness Index (SWI) derived from application of a triangle space concept between LST and NDVI data. Using satellite data of LST and vegetation index NDVI, amount of water stress during each time step was estimated from a linear relation. The new developed drought index mapped well the spatial distribution of dry periods and their intensity in the agronomy year of 2000-01. The cumulative number of dry days (SWDI<0) in the period of 2000-01 was estimated as 184 days. The results confirmed also the existence of wet periods in the year 2004-05. After comparison of SWDI variations in two areas of irrigated and dry farming, the promising results were obtained. SWDI index has the capability of drought monitoring in different time scales.

Volumetric allocations of agricultural water use in 129 agricultural plains of Iran are based upon the national codes or documents of irrigation. These documents are used by the ministries of Jehad-e-agriculture and energy for allocating agricultural water. National irrigation documents have been determined by the experts of these ministries and Iran meteorological organization. In these codes, recommended method of FAO and 25 years climatologically data of the synoptic stations of the period of 1970-1995 have been used. Since it seems a significant change on temperature, rainfall, and other parameters have been occurred during the last 15 years. These changes which may either be due to climate change or climate variability have a significant effect on agricultural water requirement. If this may be the case, a revision on irrigation codes will be inevitable. For this purpose an investigation was conducted to compare the effective meteorological parameters, reference crop evapotranspiration, and crops water requirements between last 15 years (1995-2010) data and full period of data (1970-2010) with the data of the period of 1970-1995 that irrigation codes are based on that. In this study synoptic stations of Khorasan-Razavi province which is a semi-arid region were used. The results showed that if either last 15 years data is used or full period data, air temperature has increased, relative humidity and rainfall has decreased, and radiation and wind speed have also increased. Therefore, crop reference evapotranspiration and crops water requirements have increased for most parts of the province. If full period data is used, ETo showed an increase up to 47% and if last 15 years data are used ETo showed an increase up to 48% in some part of the province. These results are an indicator for the necessity of revision in irrigation codes.