فصلنامه علوم و مهندسی آبیاری
سال سی و پنجم شماره 1 (بهار 1391)

Estimation of infiltration parameters is very difficult in furrow irrigation while they have very important effect in design and evaluation of surface irrigation systems. There are different methods for estimating infiltration parametersbased on mathematical models such as EVALUE, SIPAR_ID and INFILT. EVALUE model uses direct solution whereas two other models are based on inverse solution. The objective of this study is to evaluate these models to estimate infiltration parameters in furrow irrigation. Twelve data sets of experimental blocked-ended and free draining furrows were used in this assessment. The data sets were under different conditions, e.g. length, slope, and flow regime. Using the estimated infiltration parameters, the total infiltrated volume was predicted to evaluate the accuracy of the mathematical models. The results indicated that EVALUE and SIPAR_ID provided the lowest errors for estimating the infiltrated volume with RMSE 1.86 and 1.78 m3 at blocked furrows, respectively. At free draining furrows, SIPAR­­_ID with RMSE 1.11 m3 has the best result. The models specifically INFILT with RMSE, 1.63 m3 provided lower accuracies in cutback flow regime relative to continuous flow.

In this study, activated carbons of reed and sugarcane sawdust are used as adsorbents to remove dissolved solids from water. The objective of this research work were to various evaluate the effects of adsorbent type, amount and total dissolved concentration on the sorption capacity, sorption properties and removal efficiency of the two used adsorbents. Results of the study indicated that optimum value of sorbent was 1600 mg/l and maximum removal of TDS belongs to the sugarcane sawdust activated carbon with 75 removal percentage. The removal percentage of TDS from water by sugarcane sawdust and reed carbons, are 63 and 57 respectively. Because the materials for preparing activated carbon of sugarcane sawdust are cheep and it has high removal efficiency for TDS as a result it could be concluded that sugarcane sawdust activated carbon would be good replacement for activated carbon.

Awareness from spatial variability of quality parameters is important tool for understanding the region talent and how to manage of land. So in this research to analysis electrical conductivity and the ratio of absorption of sodium in groundwater using Earth statistical methods. For this purpose, information dependent on analysis of 169 wells of water in Neyshabour plain with climate of semi arid is based on last sampling in 1386 were used. Earth statistical methods used For Zoning parameters listed include Ordinarykriging, Logkriging, Cokriging, IDW and SPLINE model. for evaluation of methods are used from cross validation techniques with Standards of MAE, MBE, RMSE and R2 Between actual and estimated data. Studies have shown that spatial correlation in EC and SAR is so very in Neyshabour plain. Results of EC and SAR maps using Cokriging and exponential and spherical model showed areas of North East Plains, aquifer is located under the influence of surface and groundwater supply, include values EC less than 1.5 dS/m and 2.5 mg/lit, the aquifer quality in above mentioned range towards the plain central regions gradually decreased and within the granule regions of aquifer (South and West regions of aquifer) formation of the alluvium is not desirable, EC and SAR values will increase in this range is higher than 12 dS/m and18 mg/lit. Finally, the quality of Neyshabour plain groundwater from viewpoint EC and SAR in terms of impact on soil permeability was investigated. The EC and SAR anomaly maps were drawn and shown that with increasing salinity levels in water drop pezometer correlated.

Bottom rack is a hydraulic structure which is placed on the bed of mountainous rivers through which part of flow in the main channel is diverted. These structures have very wide application in industry, irrigation, drainage and etc. The present study was directed to estimate the discharge coefficient of a new kind of bottom racks including both transverse and longitudinal bars which is named "mesh panel racks" with and without considering solids in the fluid. This kind of bottom intake has advantages from structural point of view and has less deformation under static and dynamic loads. Laboratory setup with three mesh panel intakes was built and the effects of various parameters such as racks slope, porosity and geometry, sediment size and sediment grading were explored. A dimensional analysis using Buckingham theory showed the effective hydraulicand geometric factors that affect the discharge coefficient (Cd) of bottom racks. Then, a statistical approach to determine the discharge coefficient of a rack structure was developed with linear and nonlinear regression using SPSS software. Finally, hydraulic performance of mesh panel intakes was compared with and without sediment.

Soil salinity is one of the important soil properties that has a significant effect on many processes such as plant grows. The objectives of this paper are to estimate soil salinity and to map the salinity risk in Meiankangi located in Sistan plain. Soil electrical conductivity was measured on soil samples taken from 122 sites distributed radiometry across to study area. The geostatistical methods of ordinary kriging and indicator kriging were used for salinity mapping. The latter was used to map the probability that soil salinity exceeds a critical threshold. The methods were evaluated using cross-validation. The validation of used methods were evaluated using root mean square error (RMSE( and mean bias error (MBE). The results showed that both methods were similar for predict soil salinity. The probability maps of exceeding 2, 4 and 8 ds/m were generated using indicator kriging. Given the critical threshold of 2 ds/m, almost all the regions have a probability of salinity of more than 0.5. The results showed that the salinity is moderate across the study area. Overall the obtained results indicated that unlike ordinary kriging, indicator kriging is able to map the salinity risk. These maps are very helpful in decision such as land classification and management.

The major topic in the study of the compaction is the soil pore size and type. Soil compaction can be significantly reduced with changes in soil pore volume, water infiltration and availability of plants to air and water. Sum effects of the above may lead to reduced soil quality. Therefore a field study was performed to evaluate the effect of soil compaction on movement of water in the pores (coarse and medium size pores) of loamy soil. A completely randomized block was designed with three replications, applying blank (No teraffic passing), once, twice, three times, four times and eight times of tractor passings. Number of pores and percent flow through them with effective porosity and hydraulic conductivities (saturated and unsaturated), was determined in the field using disc infilterometer in four potentials (0, -3, -5 and -15 cm of water). Our results revealed thatin all of the treatments medium size pores were many times of large ones hence, both sizes decreased with compaction. Results of disc Infilterometer showed that coarse and medium size pores (macro and meso pores) of eight times tractor passings relative to control decreased 85 and 62.5 percent respectively. The majoreffect of compaction was onthelarge size pores. The mediumpore sizewasmore impressed than large pore size. Number of medium poresin the soil was less than large ones.

The aim of this study is trend analysis of streamflows of east Azarbayejan in three time scales, which are monthly, seasonal and annual using the non-parametric methods. For this purpose the information of discharges of ten hydrometric stations (1983 -2008) were used. The Mann-Kendal test was used after removing the all significant autocorrelation effects from the data. In order to estimate the slope of trend line the Sen,s estimator method was used.Results showed that about 30% of the stations showed statistically significant negative trends in annual time scale. The strongest negative trend line slope belonged to the Vanyar station having the slope of 0.35 (m3/s/year) in annual time scale. In seasonal time scale, negative trends observed at almost all the stations. In monthly time scale streamflow trends were negative for most of the stations and none of the stations experienced positive significant trends (even at 10% level). The strongest negative trend observed in Tazekand (Soofi-Chay), which was significant at 10% level.

One of the most effective parameters in discharge prediction especially in snowy basins, is the snow parameter. Snow water equivalent (SWE) is the most common parameter used in modeling river flow to take the effect of the snow on the model into account. In this research, according to unavailability of the SWE parameter in most of the basins, we tried to offer Cprecip and MAZ-Cprecip instead of SWE. Cprecip is cumulative precipitation from November 1st to April 1st indicating the snowpack amount melting in the spring. MAZ-Cprecip is received by giving some changes on the Cprecip (to be suitable with Mazandaran basins). The results showed that the Cprecip parameter can be replaced with SWE and that MAZ-Cprecip parameter is more efficient than Cprecip parameter in Mazandaran basins, due to its most conformity with the basins in this region.

A bivariate extreme value distribution, namely the Gumbel mixed model constructed from Gumbel marginal distributions is employed to analyze the joint distribution of correlated flood peak (probable maximum flood) and amount. Based on its marginal distributions, the joint distribution, the conditional probability distribution, and the associated return periods can be deduced. Parameters of the bivariate distribution model are estimated based on its marginal distributions by the method of moments (MM). The usefulness of the model is demonstrated by using it to represent multivariate probable maximum flood events at the Beheshtabad basin discharge station Armand in Iran.

The frontal of gravity current is most important section of these flowtypes. The advance force in front is pressure gradient due to density differences betweenfront flow and ambient fluid. In order to find the roughness effects as a resistor on frontal velocity, a series experiment of saline gravity currents were performed on rough beds with size of 0, 4, 7.5, 12 and 15 (mm). The saline gravity current with three inflow discharges of 0.7, 1 and 1.3 (lit/s) and three concentrations of 10, 16, 20 (g/lit)was flowed on slope beds from 0.05 to 2.2 steep percentage. For estimation of frontal velocity and assessing effects of parameters, a linear model by correlation coefficient of 0.9 and RMSE of 0.037 and mean ratio deficit of less than 10% was derived. By applying of linear modeling and linear standardization data, the efficiency index of slop, relative roughness and non-dimensional discharge (Richardson number) on prediction of non-dimension frontal velocity was estimated as 0.17,-0.50 and -0.35.