Study of Soil, Water, and Cropping Pattern in Danastar Wah (Manchar Lake) Command Area Using Geospatial Tools
Authors: Siyal A.A., Lakhair I., Babar M.M., Siyal P., Solangi G.S
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The effluent water brought by RBOD (Right Bank Outfall Drain) is not only threat to the aquatic life of Manchar Lake but also the fertile agricultural lands which are being cultivated by use of lake water through Danastar Wah are at risk of salinization. The farming community of the area is scary of continual use of irrigation waters received through the Danastar Wah; they are of the view that the constant use of this water will ruin their fertile lands into salt-affected soils. Thus, keeping in view the fears of the farmers of the command area of Danastar Wah, a study was carried out to investigate the water quality of the Manchar Lake, RBOD MNV (Main Nara Valley) drain and Danastar Wah, and to examine soil salinity status of the area using Geo-referenced field and satellite imagery data for Kharif season of the year 2015. The results of the study showed that the EC (Electrical Conductivity) of the Danastar Wah water was below 1.2 dS/m. Thus, the water was suitable for irrigation purpose. In all the water samples, Na+, Ca2+ + Mg2+ and CO3 concentrations were found within the permissible limits, while no concentration of HCO3 was found in any of the water samples. In the command area, clay texture was dominant down to a depth of 60 cm soil profile. In the area about 37, 28, and 30% of the soils were normal (non-saline), saline and sodic, respectively; while only 5% of soils were saline-sodic. The cotton crop was identified as the major Kharif crop, occupying about 13.76% (2,844 ha) of the total command area, followed by rice crop grown on about 5.21% (1,078 ha) of the command area. The overall accuracy of image classification was 90% with a kappa coefficient of 0.86. Based on this study, it can be concluded that the water of the Danastar Wah can be used for irrigation purpose during Kharif season only with the condition that adequate land drainage is maintained. It is also suggested that before using the water of Manchar Lake, RBOD and Danastar Wah for Rabi season, analysis for water quality be conducted. GeoInformatics (GIS and RS) tools can be employed for spatial and temporal monitoring of water quality of the Manchar Lake.