Iranian Journal of Irrigation and Drainage
Year:2010 | Volume:4 | Issue:2|Papers Count:19

Outdoor study was done in 2004 (1384) in farms with 2 meter drain spacing and 15centimeters drain depth and without drainage in 4×10 basins in Rasht - Rice Research Institute of Iran (Rasht). In this study fluctuation of water table depth during growing season was measured in respect of weather condition. Consequently DRAINMOD model was run to evaluate and predicting water table depth in physical condition and boundary value of the site. Because of the canola’s negative response to water logging, predicting of water table is important. Indeed a model can be used for predicting various   processes and as a management tool, when it is evaluated in the region. Results indicated that DRAINMOD was successful in predicting water table fluctuations. Evaluations in predicting daily water table depth showed that the root mean square error (RMSE) was about 8 centimeters in both treatments. Results also indicated that the potential of the model in predicting water table depth toward measured water table depth was about 4% in surface drainage treatment and 17% in without drainage treatment. Precise information on deep seepage is operative to improvement of estimation of the model.

In order to study of the effects of plastic mulch and water quantities in two drip irrigation methods (surface and subsurface) on water use efficiency, quality and quantity yield of melon (ghasri variety), an experiment was carried out using a split split plot base on randomized complete block design with 3 replication in Khorasan Razavi Agricultural and Natural Resources Research Center (Torogh station), for tow years (2006 and 2007). In this experiment there are 12 treatments. The main-plots were divided into 3 levels of irrigation: A1= 100, A2= 80 and A3= 60 percent of water reqirement. Sub-plots were 2 drip irrigation methods (S1= surface and S2= subsurface lateral of type) and 2 kind of mulch (M1 and M2 was with and without black plastic mulch). Experiment results showed that, in the first year, the average yield of irrigation treatments of A2 to A1 and A3 to A2, decreased 10 and 16 percent respectively and in the second year, decreased 13 and 32 percent respectively. The average yield of surface drip irrigation was more than subsurface irrigation and when used of black plastic mulch, the mean yield increased but there was not significant different. There was not significant difference between numbers of melon in surface and subsurface lateral drip irrigation, soil with and without plastic mulch treatments. The mean of water use efficiency (WUE) increased when reduced water irrigation. There was not specific result in quality of melon, because the effect of treatment on quality in first year was not similar to second year. In general, subsurface irrigation treatments (80 percent of water supply) and plastic mulch, with the economic rate of 350 percent, was the best treatment.

Wetted front placement is important in optimal irrigation system design. Wetted pattern depends on emitter discharg, application time, total volume of applied water, soil texture and lands slope. Maximum wetted area is cosiderd 15 to 30 cm, generally. to investigate slope affects on the maximum wetted area and wetted soil volume, a field study was conducted in a silty clay loam field with 4 different slopes of 0, 5, 15 and 25%, emitter discharg of 2,4 and 8lit/hr and application times of 2 and 4 hr. Wetting pattern dimensions was measured by excavation sections parallel to the surface, 24 hr after finishing irrigation. By result of this study, the equation which is generally used to estimate the maximum wetted diameter, adjusted in silty clay loam sloping lands and decreasing emitters distance in single line system in the slopes more than 10% suggested. Also 2 methods used to determining wetted soil volume.

Infiltration process is one of the most important components of the hydrological cycle. The importance of the infiltration process has enforced the soil and water researchers to model this process for quantitative applications. In this study, the performance of Green and Ampt, Philip, Kostiakov, Kostiakov-Lewis, Soil Conservation Service (SCS) and Horton infiltration models under different soil texture classes and different land uses were evaluated. For this purpose, the infiltration data were obtained by double rings method from 210 point of different regions in Iran. The parameters of these models were then obtained, using least square optimization method. In order to evaluate the accuracy of the models, the mean error (ME), root mean square error (RMSE), mean absolute of mean error (MAME) and Pearson correlation coefficient (r) statistics were calcualted. The results indicated that, compared to other models, the performance of Kostiakov-Lewis model had more consistent trend in estimating the cumulative infiltration under different study regions. This model provided first ranking of evaluation in different soil texture classes and land uses. The results indicated that Horton, Kostiakov and Philip models underestimated the infiltration process while Kostiakov-Lewis, Soil Conservation Service (SCS) and Green and Ampt models overestimated the soil water infiltration process. In the most soil texture classes and land uses, the Kostiakov-Lewis and Horton models were systematically over-estimator and under-estimator models, respectively. The results of this study indicated that compared to the other infiltration models, the Kostiakov-Lewis model is the best model for quantifying the infiltration process.

Spatial variability of infiltration has an important role on the hydrological processes. Spatial variability of infiltration is affected by extrinsic and intrinsic properties of soils. The objective of this study was to investigate the spatial variations of infiltration parameters through the variation of soil intrinsic properties and land use variation (as an extrinsic factors) using geostatistics methods. Therefore, 95 single ring infiltration data were measured from a field with rangeland and degraded rangeland land uses, simultaneously. The parameters of the Philip model were then obtained using measured infiltration data for all sampling points. The spatial variations of the parameters were assessed using the whole measured data and measured data at rangeland land use, separately. The mean infiltration data in the rangeland land use were higher than the degraded rangeland. It seems that cultivation activities that led to degrading in the rangeland are one of the reasons for decreasing the infiltration at the degraded rangeland comparing to protected rangeland. The geostatistical analysis indicated that strong spatial variability in Philip parameters exist in the investigated area, such that about 10 percent of saturated hydraulic conductivity variation and 35 percent of the variation in sorptivity parameters was random in the rangelands. The variography of the parameters showed that the land use change affected saturated hydraulic conductivity parameter more than sorptivity parameter, so that results on decreasing the spatial structure of saturated hydraulic conductivity and sorptivity parameters from 89 and 64 percents to 56 and 53 percents, respectively. The comparison between the result of this study and the past study showed that the spatial variability of hydraulic conductivity depend on the study area. The results indicated that the geostatistics method was a proper method for predicting the infiltration parameters in the study area with 0.08 and 0.19 RMSE for saturated hydraulic conductivity and sorptivity, respectively.

Crop evapotranspiration (ETc) is one of the main factors essential for the assertion of water and energy balances at the earth surface. Although, the input parameters required for the estimation of ETc are spatially and temporally variables, ETc is usually estimated by reference evapotranspiration models that are locally calibrated and are site specific and then adjusted by implementing crop coefficient (Kc) to include the effects of a specific crop. The objective of this research was to investigate the feasibility of using time-series MODIS 250 m Normalized Difference Vegetation Index (NDVI) datasets in conjunction with ground data (climatic parameters) to calculate actual wheat crop coefficient in a large scale area (i.e., Gorgan Rod watershed) during wheat growing season. The results indicated that the annual actual wheat evapotranspiration derived from remote sensing as compared with FAO-penman-monteith equation had RMSE, MAE, ME and E of 18 mm, 16 mm, -1.1 mm and 1.91 percent, respectively.

Saturated hydraulic conductivity (Kfs) is one of the important physical features of soil that have wide usage in soil and water science. It is one of the important parameter in the irrigation and drainage, ground water flow, some of the road and structure project, river engineering etc. Kfs is the important parameter on cost of the projects so it is very important to achieve with most accuracy. The determination of Kfs has divided in two ways: laboratory and outdoor way. Outdoor way done in above or under the ground water, depend on the ground water depth. Guelph permeameter (GP) method has done on above the ground water. The GP method has a good accuracy in determination of Kfs. However, C is an important parameter in the two head GP. C is calculated with five methods (Pourshe, Pressure, Glour, Half-source and Numerical). Only problem of GP are the negative results that may have seen in some results. In this research the GP experiments were down with different ratio of H2/H1 in 18 holes (Max and Min H are 5 and 20 cm, respectively). Then Kfs and fm (matric flux potential) are determined by two head analysis of GP with different solution methods for well shape factor (C). Result showed if the Pourshe method was used for C factor calculation, negative results have been minimized and other methods for the C calculation (Pressure, Glover, Numerical and Half-source) have been produced low to high negative result of Kfs respectively. Pourshe and Pressure methods for C calculation cause the maximum negative result of fm respectively. So, three other methods of C calculation are suitable for determination of the fm. However, number of negative result for Kfs and fm are decreased when the  increase.

Polyethylene mulch usually decreases water evaporation from soil surface, control weeds and increase yield crops. In order to study the effects of black mulch on tomato yield, yield components and water consumption efficiency an experiment was conducted in Kahriz Station (Urumia, Iran) for two years (2005-2007). The experiment was carried out at split plot factorial in CBR design with four replication in a loamy silt soil. Experimental treatments were row spacing (100 and 120 cm), in-row spacing (30 and 40 cm) and black plastic. The treatments of black plastic were: full ridge and half furrow were covered by mulch; full furrow and half ridge were covered by mulch and control (no mulch) respectively. Each plot was irrigated separately. The results indicated that mulch was effective on yield and yield ingredients (weight fruit and fruits number per plant) and interaction on yield ingredients at 1%. The best treatment of mulch for yield increase, earliness and weed control was full ridge and half furrow. Interaction of plant density and mulch affected only earliness and stem length. Water use effeciency (WUE) was increased by using mulch. Water decreased 28.8 % and 41.3 % in full ridge and half furrow and full furrow and half ridge respectively in comparison with control. The best treatment according on WUE was full furrow and half ridge covered by mulch and 100×30 sowing pattern with 33 kg.m3.

Accurate irrigation planning needs soil water content monitoring. Determining of soil properties, such as soil water content, that show spatial variability,  in form of a global quantity and neglecting its spatial variability, is not adequate for site-specific-management. In this study, the estimation and mapping of soil water content, in field capacity (FC) and permanent wilting point (PWP), were compared by global mean, inverse distance weighting (IDW) and ordinary kriging interpolation methods. Results showed that a clear spatial structure could be identified for both FC and PWP. Estimation accuracy increase for using of global mean, IDW and ordinary kriging methods respectively. These results suggest that kriged maps can be used for irrigation planning programs because as more accurate interpolation from water content at FC and PWP.

In this paper, the geometrical similarity of scour holes downstream of a sluice gate is studied experimentally. Although, nowadays a comprehensive understanding on scour of noncohesive sediments is attained, because of the complex nature of clay minerals, the scour of cohesive sediments has received less attention. 36 experiments with 12 hours run time, was carried out in a rectangular flume of 9 m length, 0.6 m height and 0.5 m width. Six mixtures of cohesive and noncohesive sediments with different fractions of clay minerals ranging from 10 to 40 percent were tested. The results show that the scour profiles are nonuniform across the flume width. Despite the noncohesive sediments, the scour hole in cohesive beds could not be introduced as a unique equation. Therefore, three different types of scour holes are distinguished and in each case, graphs and equations are presented to determine the shape of the hole. Also, a novel equation is proposed to calculate Bw parameter which is used to nondimensionalize the scour hole. Finally, the effect of tailwater depth is investigated.

Water shortage has always been the main limiting factor of agricultural development in arid and semi-arid areas. Therefore, the improvement of the water use efficiency (WUE) has high importance in these areas. The simulation models of yield response to the water are expected to play an increasingly important role in the optimization of water productivity (WP) in agriculture. The AquaCrop model, which has recently been developed by FAO, predicts crop productivity, water requirement, and water use efficiency for different scenarios including water-limiting conditions. This model requires to the evaluated for different regions and crops. In this research the potential of AquaCrop model in simulating the yield response to water availability for wheat in Karaj climate was studied. For this reason, six irrigation treatments (20, 40, 60, 80 and 100% of the water requirement and single-irrigation) were studied. Results revealed that the model performed satisfactorily in simulation of grain yield, water use efficiency in all of the irrigation treatments with irrigation intervals of 7 days, but it was less satisfactory in simulating treatments with irrigation intervals of 14 days. In addition, results showed that the model didn't have a good performance when osmotic pressure of soil increased (when soil water content declined). However, the easiness of the AquaCrop model, the limited number of to input parameters, and the sufficient degree of simulation accuracy make it a valuable model for estimating crop productivity under different irrigation water levels conditions, supplementary and deficit irrigation, and on-farm water management strategies for improving the efficiency of water use in agriculture.

Because of unsuccessful performance in most of irrigation and drainage networks, it has become more essential to assess the performance of such systems more than it used to be. The objective of the present study is to investigate the importance of effective criteria on performance of irrigation and drainage networks. For that, a combined promising framework, Analytical Hierarchy Process (AHP) and TOPSIS technique, is considered. The survey is accomplished on the triple regions of Sefidrood Irrigation Network. Five attribute decisions include technical, management, environmental, economic and social criterion are considered as decision criteria and for each of them, 6, 7, 3, 8, and 3 sub-criterion are selected, respectively. The criteria and sub-criteria weights are computed using Expert Choice software by AHP method. Relative importance of each sub-criterion on the alternatives (Irrigation regions) is also calculated by TOPSIS technique. Results indicate that the management criterion by relative weight of 0.384 has the greatest impact and environmental criterion by relative weight of 0.09 has the lowest impact on the performance of the proposed irrigation network. Also, the efficiency of infrastructures and water cost attributes by weight of 0.085 and 0.007 have the most and less importance impact, respectively. Results reveal that Foomanat region by aggregate weight of 0.555 is the most efficient irrigation region and Markazi region by weight of 0.446 assigned the most unsuccessful performance among Sefidrood irrigation network regions. The sensitivity analysis demonstrates that the rank of irrigation regions may be changed as affected by reducing relative importance of technical and management criteria and increasing economic and social criteria. The proposed approach can synthesize various sets of criteria in the preference elicitation of performance, valuation and comparison of irrigation systems and their different parts.

In order to investigate the effects of limited irrigation (LI) scenarios on bread rainfed wheat (Triticum aestivum L.) on-farm experiments were conducted during the 2005-08 cropping seasons at multiple farms across benchmark watershed of Honam (Lorestan Province) in the upper KRB. The treatments included two main management (Traditional and advanced management) and four levels of limited irrigation (Rainfed, single irrigation of 50 mm at spring time, single irrigation of 75 mm at planting time and 125 mm irrigations at planting and spring times). The results of this study showed that under rainfed conditions, wheat grain yield of  (2269 kg ha-1) increased by 33% as compared to TM (1726 kg ha-1). The optimal program was a combination of advanced agronomic management with LI options (single irrigation at planting time / or spring time). At this preferred program, maximum water productivity and net benefit were obtained. At rainfed conditions RWP of traditional management (0.35 kg m-3) increased by 28.6% as compared to advanced management (0.45 kg m-3). The results showed that a single irrigation application at sowing or spring time (during heading to flowering stage) increased total water productivity (TWP) of wheat to an average range of 0.57 to 0.63 kg m-3 over the three growing seasons. The average irrigation water productivity (IWP) of wheat reached a range of 2.15-3.26 kg m-3 by using single irrigation at sowing or spring time. Supplemental irrigation at critical stages (planting time/or spring time), deep root expansion, incrassating green canopy cover and its influence on evaporation control, were main reasons on effectiveness of limited irrigation. Low RWP (and yield) in farmers’ practices were mainly due to suboptimal agronomic management practices. These preliminary results confirm the potential of single irrigation and early/normal planting as an effective scheme to enhance productivity.

In order to optimize irrigation water use in a sustainable agriculture different approaches are implemented. One of these methods is based upon the water extraction from soil. This methos is applicable if the amount of water needed by plant is measured by lysimeter or calculated by real time climatic data. In order to compare the differences between using 1- on farm real time data, 2- real time data from a climatic station outside and far from the field, and 3- using average data of meteorological data of the region an experiment was conducted on fodder corn crop in Karaj. Farms of cron were selected close to each other and were irrigated by similar centerpivots. In one the systems sencors were placed and meteorological parametes were measured. The system itself calculated evapotranspiration durin one cycle and replaced the same amount of water which has been evaporated. In other system this action was manually don by daily meteorological data of Karaj climatic station. The third farm was irrigated based on regional average data of meteorological station of Karaj. The results showed that in first trial 6838 cubic meter of water was used and and 78 tons.ha of cornwas harvested. Therefore water applicatioc was 11.4 kg/mÙ3. The results for second and third trial were 7640, 78.2, 10.2 and 9350, 79.9, 8.5, respectively. This showed that if real time and on farm data of meteorological parametes are used for calcuilating irrigatin needs, yield could be increased by 27 percent.