Assessment, Spatial Variability and Mapping of Some Water Quality Parameters for Use in Drip Irrigation Design in Lordegan Plain, Iran

Generalizing point measurements of water quality characteristics to maps can be useful for estimation purposes. Interpolation techniques may be used to estimate unknown parameter values. Such characteristics as EC, TDS, turbidity, TSS, pH, and Langelier Saturation Index (LI) play a role in drip irrigation system design. In this study, the spatial patterns of these water quality parameters in the Lordegan plain located in Charmahal-va- Bakhtiari is investigated using geostatistical interpolation techniques of kriging and inverse distance method (IDM). For this purpose 52 agricultural wells, well-scattered across the plain, was sampled four times during year 1389 and relevant water qualities were measured. For all studied parameters, kriging had a lower ME and R2 compared to IDM and was, therefore, selected for mapping. EC values were between 450 to 960 μS/cm that placing water in class C2 and C3 for irrigation. TDS in northern part of the aquifer reaches 500 mg/L which presents medium clogging risk in drippers. LI index was always positive ranging from 0.08 to 0.17 with a mean of 0.12, therefore indicating a slight potential for calcium precipitation in drip irrigation system. The presence of carbonatic geological formations in the plain may be the main reason for positive LI index. Overall, the values of water quality parameters in the northern part of the plain tended to be higher than in the other parts of the aquifer. Therefore, in the northern part of this plain there exist some restriction for drip irrigation and slight risk of system clogging. Overall, the water quality of this aquifer is suitable for drip irrigation particularly in the eastern and western parts of the aquifer.