Mina Taheri; Vahid Rezaverdinejad; Javad Behmanesh; Fariborz Abbasi; Javad Baghani
Abstract
Water resource deficiency and the necessity of sustainable production in irrigated lands have attracted much attention to water productivity issues. In this regard, analysis, estimation, and preparation of water productivity map are necessary as an influential factor to recognize cultivation potential ...
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Water resource deficiency and the necessity of sustainable production in irrigated lands have attracted much attention to water productivity issues. In this regard, analysis, estimation, and preparation of water productivity map are necessary as an influential factor to recognize cultivation potential in irrigated lands. The aim of this study was to select a proper interpolation method for water productivity and investigate spatial changes in water productivity in Iranian wheat production centers. In this research, 241 field data were used, of which range of water productivity (irrigation water + effective precipitation) was estimated between 0.3 to 2.58 kg.m-3 with the average of 0.79 kg m-3, in 2016-2017 season. Interpolation methods used included Ordinary Kriging, Inverse Distance Method (IDW), and Radial Basis Function (RBF). Cross Validation technic was applied to evaluate methods by statistical measures such as Root Mean Square Error (RMSE), Mean Bias Error (MBE), and Mean Absolute Relative Error (MARE). Interpolation methods evaluation showed that between available procedures, typical Kriging method with exponential semi-variogram model had the most proper condition to prepare wheat water productivity zoning map. The results of the spatial analysis of water productivity confirmed that geostatistics could be used with acceptable accuracy (MBE=0.005) to provide water productivity mapping. Results of Cluster analysis of the effective factors (salinity of irrigation water, soil salinity, and crop cultivar) on wheat water productivity index showed that the areas suitable for wheat cultivation were separated into 13 independent groups (at the 5 percent level), such that the highest and lowest mean water productivity of wheat were observed in group 5 (Mean = 0.84 kg.m-3) and group 10 (Mean = 0.41 kg.m-3), respectively.
s heshmati; h beigi
Abstract
Groundwater is the only important water resource for irrigation in the Shahrekord plain. Due to over-extraction, the water-table is continuously declining. Drip irrigation has the potential to save water. The main aim of this research was to ...
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Groundwater is the only important water resource for irrigation in the Shahrekord plain. Due to over-extraction, the water-table is continuously declining. Drip irrigation has the potential to save water. The main aim of this research was to investigate the spatial variability and mapping of irrigation water quality of the Shahrekord aquifer. Ninety-seven agricultural wells were sampled three times during 2010 and samples were analyzed. Electrical conductivity (EC), total dissolved solids (TDS), total suspended solids (TSS), and pH were measured and the Langelier index (LI), sodium adsorption ratio (SAR), permeability index (PI), residual sodium carbonate (RSC) and sodium percent (Na%) of each sample were calculated from the measured parameters. The averages of the three samples have been presented here. The mean EC and TDS were 456 µS/cm and 296 mg/l, respectively, placing the groundwater in, respectively, good and relatively good classes for irrigation. According to Wilcox's diagram, almost all groundwater samples were designated as C2S1. Shahrekord groundwater is suitable for irrigation based on Na%, RSC and PI, too. Based on mean pH and TSS of, respectively, 7.6 and 70 mg/l, Shahrekord groundwater has medium potential for dripper clogging. Spatial variability of EC and TDS was best described with a Gaussian model while the other parameters were best described with spherical models. Comparison of the observed and mapped correlations indicated the suitability of the selected variograms and the Kriging method for mapping of parameters. Maps showed that the values of measured and calculated parameters were higher in the southern part of the aquifer. Based on the EC map, the groundwater in most parts, except the southern part of the aquifer, was classified as good and very good. Only in the south of the aquifer did TSS reach 512 mg/l, indicating a medium physical clogging potential in drip irrigation. The pH and TSS maps indicated a medium potential for clogging of drippers, generally across the aquifer. At the same time, the Langelier index across the aquifer was generally negative, indicating the suitability for drip irrigation. The positive LI in some areas of the aquifer may be due to the existence of carbonatic formations and their solubility.