مجله پژوهش آب ایران
پیاپی 2 (تابستان 1387)

The aim of applying water stresses are two fold: a) to enhance Water Use Efficiency (WUE) and, b) to reach optimum-agronomic objectives (including, enhancing certain qualitative parameters of the crop, preventing excessive growth of aerial shoots of crops like sugar beet, etc.). This study was performed to evaluate the effect of irrigation interrupting time and its influence on the quality and quantity of sugar beet. The experimental design used Completely Randomized Blocks (CRB) methodology with 5 treatments; one to five weeks irrigation interruption before harvesting. Each treatment was planted on 5 lines with a 7 m length. The row spacing was 60 cm and the plants were 20 cm apart. The results of simple and combined analysis of variance in twoyears for different traits (root yield, impure sugar yield and white sugar yield, sugar content) showed that there is no significant impact by varying the parameters within the 5% statistical variance. Also, results of mean comparison for white sugar yield in the combined analysis proved that the greatest yield belonged to the 4th and 5th treatments with 9.11 and 9.12 ton/ha, respectively. Therefore, there is no significant difference regarding characteristics studied in statistical group, though even in some cases water stress can improve quality and increase sugar content percentage. So, irrigation interruption 4-5 weeks before harvesting in October can be suggested.

Water discharge is one of the main components for planning, management of waterresources as well as studies of reservoir operation. Therefore it is necessary to use somemethods for forecasting by disaggregation hydrological variables into finer time scales. In this research, artificial neural networks (ANN) have been used for disaggregation of annual into semi-annually and monthly series, disggregation. The models were basic, extended and feed forward back propagation (FFBP). Lake Uromiyeh river basin was selected as a case study for this study which is situated in North West of Iran. Streamflow data were taken from the rivers in the basin. Statistical measures including RMSE, MRE, and SE were calculated to investigate the accuracy of the results. The results indicated that the ANNs and extend models have better performance than basic model for seasonal streamflow forecasting but in smaller scales the extended model is recommended. Results indicated that the differences between observed and disaggregated streamflow series have been increased by presence trend in forecasted values because the effect of parameter estimation step. The statistical properties of variables like mean and standard deviation are also preserved using these models.

Almost two-third of demand water of Zayandehrud basin, which is equal to 3500 million cubic meters, is supplied by groundwater, especially by wells. This water is used mainly for irrigation.Because of recent droughts and consequent decreased discharge of Zayandehrud, demand for groundwater has increased, leading to a sharp decline of groundwater levels in most of plains of the basin. Statistical analysis of meteorological data and pizometric wells shows a downward trend of drawdown of water table continues. This situation has created difficulties for developments of province Isfahan. So, it is urged to both decrease groundwater abstraction, and increase water productivity. To reach this objective, it would be useful to estimate the monthly abstracted groundwater in the irrigation networks. In this research, the necessary maps were prepared by using data collected from wells, questionnaires addressing the farmers, and Ilwis software. These maps once were superimposed, served to convert the annual abstracted well discharge in plaines to monthly abstracted discharge in the main irrigation networks. Finally, the gross rate of annual and monthly consumed water per hectare was obtained for irrigation networks of right bank of Nekoabad, left bank of Nekoabad, right bank of Abshar, left bank ofAbshar, Mahyar-Jarghooyeh, Borkhar and of average of total networks. The rate of annualconsumed water per hectare during agricultural year (Oct. 2003 to Oct. 2004) estimated for the mentioned networks were: 15011, 7014, 11509, 4952, 1444, 2662 and 5302 m3, respectively. These values may vary following climatic conditions, crop pattern and other parameters. Meanwhile their initial estimations and their comparison can help to improve water productivity in this basin.

In this study, regression equations were derived for estimation of sequent depth ratio and relative jump length in gradually expanding stilling basin with trapezoidal and rectangular cross sections.Non-dimensional parameters were derived from the effective parameters in hydraulic jump using Buckingham π-theorem. Finally, 5 arrangements of parameter for estimation of sequent depth ratio and relative length of jump in trapezoidal stilling basin and 5 arrangements for the estimation of sequent depth ratio and relative jump length in rectangular basin were generated.The best equations for the sequent depth ratio and jump length were selected by comparison between the models, using R2 and RMSE. The best equations to estimate the sequent depth ratio and relative jump length in gradually expanding stilling basin with rectangular section were found with R2=0.989, EF=0.9895, RMSE=0.21264 and R2=0.951, EF=0.9528, RMSE=0.001949 respectively. By the same way, the best equations for estimation of the sequent depth ratio andrelative jump length in gradually expanding hydraulic jump with trapezoidal section were found with R2=0.964, EF=0.9654, RMSE=0.318 and R2=0.951, EF=0.9505, RMSE=3.159 respectively.Evaluation of the models with the experimental data shows that the models can fairly predict the characteristics of expanding hydraulic jump in rectangular and trapezoidal cross sections.

Cotton is a water intensive plant which reacts to both quantity of water and method of irrigation at different growth stages. Because of developing sprinkler irrigation systems in recent years, it is necessary to compare sprinkler and conventional surface irrigation methods in different growth stages of different crops like cotton. Experiments were carried out between 2003 and 2005 using split plot designs which were repeated three times. Irrigation treatments in different growth stages were main plot and cotton varieties of Sahel and Sepid were taken as sub plot. The composite analysis results of cotton yield showed that there No significant difference between the annual yields. However, There was significant different on cotton yield and boll weight of irrigation treatments while, the different between the earliness percent and boll number per plantwas not significant. The highest yield obtained in furrow irrigation compared to sprinklerirrigation was an extra 19.3% yield. There was significant different between two cultivars on view of cotton yield and yield components so that Sepid had 8.3% higher.

In order to calculate the effects of using treated municipal wastewater on Seed Yield and its Components in sunflower, this experiment was conducted in 2003, at experimental farm in south treatment plant in Isfahan. The experimental was randomized complete block design with five treatments and tree replications were used. Treatments were: Furrow irrigation with well water (FIN), surface drip irrigation with wastewater (SDI), subsurface drip irrigation with wastewater in 15cm depth (SDI15), subsurface drip irrigation with wastewater in 30cm depth (SDI30) and furrow irrigation with wastewater (FIW).Results show that, subsurface drip irrigation with wastewater in 30 cm depth as compared to other treatments, had higher seed yield and had seen noticeable difference. Also SDI15 and SDI30 treatments had higher 1000-seed weight and deaf percentage and had seen significant difference. Thus, furrow irrigation with wastewater (FIW) had lower Seed yield and 1000-seed weight as compared to other treatments. Also because ofdepending seed oil to Genes, treatments had no significant deference in this character. In SDI30, plants absorb water and essential elements, better than other treatments because water source is near the root zone. In conclusion application of treated municipal wastewater caused better yield growth compared to well water. Also because of the better soil moisture and nutrient available at root zone, application of wastewater with subsurface drip irrigation system at 30 cm depth, provided the highest yield.

In order to study the effects of wind velocity, operating pressure, various sprinkler layouts and spacing on water distribution uniformity in sprinkler irrigation system, a research project was conducted under three different wind velocities (0 - 5, 5 - 7, and > 7 m/s), using three operating pressures (35, 40 and 45m), three spacing on the lateral pipeline (15, 18 and 21m) and three different layouts (square, rectangular and triangular). Simulation experiments were conducted to estimate the water distribution uniformity. The results indicated that the distribution uniformity coefficient decreased with increasing of wind velocity. With the increase of wind velocity up to 7 m/s, the decrease of uniformity coefficient was not significant (the coefficient was reduced by 20% in the range of wind velocity applied). The highest water distribution uniformity coefficientoccurred for 15×15 m spacing while the lowest value was achieved for the spacing of 21×21 m and sprinkler spacing to spraying diameter of 0.5×0.5. With the increase of sprinklers spacing to the spraying diameter, uniformity coefficient is reduced, especially at higher wind velocities, therefore at higher wind velocities, it is recommended to reduce the sprinkler spacing to spraying diameter ratio and use square arrangement in order to achieve an acceptable uniformity.