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DEM for locating areas for groundwater recharge
maximum relief (between 230m to 300m above MSL), while the northeastern part shows minimum relief (between 210 to 205m above MSL). In rest of the area, topography is undulating and elevation values
Fig 1 Index map of the study area
range from 210m to 230m above MSL. In general, the regional slope of the area is towards northeast. DEM has highlighted some specific information about the topography, such as:
- Presence of two prominent topographic depressions, namely Najafgarh and Mundhela Depressions (ND and MD, Fig 2) occurring in southwestern and western part of the area. Both the depressions are located within the alluvial plain and have elevation values below 210m
- Red and Orange zones have maximum topographic gradient (structural ridges), Yellow zone, surrounding structural ridges has medium to gentle gradient (pediment zone), while the Blue zone has very low topographic gradient (alluvial plain)
- The DEM shows that the slope of the area due west of the structural ridge starts from east to west towards the Najafgarh drain, which latter changes to northeast towards Moti Nagar (Fig3)
- Careful observation of DEM shows that Najafgarh drain continues to flow in a northeasterly direction in spite of slight increase in topographic gradient between Ranhuala and Shastri Nagar. For instance, near Ranhaula, drain enters into light blue zone (210 - 212m), then near Motinagar it enters into green zone (212m - 215m) and finally joins Yamuna river again passing from light blue zone (210m-212m) near Shastri Nagar. Therefore it is evident that the Najafgarh drain has been constructed by cutting the upland in the light blue and green region from Ranhaula to Shastri Nagar through Moti Nagar (Fig 3)
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