Application of remote sensing and GIS in micro-watershed management -Part 1

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Study site- Sahstradhara

Introduction:

This small spot of tourist as well as scientific attraction is situated at a distance of 14 kms from Dehradun, Sahastra Dhara, literally means the ‘thousand fold spring’. The main attraction of this place for tourists is a sulphur spring which is said to possess medicinal properties and cure skin infections. Visitors often take a dip in the spring.  However for scientific studies this place is also a good spot showing aquifers, caves, recharge zones, springs and many more essential things.

Different spots of halt and observations there:

Rispana Pool: On our way to Sahastradhara, we stopped at a bridge which crossed the Rispana Nadi. This river, which provides half of Dehradun’s drinking water, was in a very sorry state. It was a site of abundant pollution; both air as well as water pollution. There were lime kilns lining the banks of the river and human settlements had also encroached upon the river bed. The air pollution was characterised by Carbon monoxide, Carbon dioxide, Sulphur dioxide, oxides of Nitrogen and Suspended particulate matter. The water pollution was characterised by almost stagnant water, eutrophication and blackish coloured water with algal bloom at places.

Spot 1, Baldi: This was our first place of hault which was close to a hair pin bend at Kulhan Karanpan and provided a very sweet panoramic view. Through this place, passes the Main Boundary Fault which separates the Shivaliks and the lesser Himalayas. The Shivaliks are younger (15 to 25 million years old) and generally made of sandstone. The lesser Himalayas are older (about 500 million years old) and generally made of limestone. Also the Himalayas are found above 6000meters of height whereas the Siwaliks are between 3000metres. On the basis of vegetation the Lesser Himalayas have a mixed type of vegetation whereas the Siwaliks have basically Sal vegetation.

On the upper side of this spot is present the village of Brahmpuri. From here, we could see the terracing of the hill slopes, both manmade as well as natural. The natural terracing was made due to the down cutting of the river Bandal. We were also able to observe the river gradient to be around 200m per km. On the banks of the river we could see Shimul trees (Bombax ceiba) which were in flowering conditions and rounded rocks due to erosion.

We were able to observe river corridor features such as ‘Fluvial Terrace’ which were flat and large in structures. At some places we were able to see ‘Paired Terraces’ which are same gradient terraces on both sides of the river.

From the top view we also could see that how the people of that village diverted canals from the main river for their utilization purpose. At a short distance from the point we could even see abandoned mines and resultant fresh landslides.

Spot 2, Kali Rao: As the name indicates, it’s a dead river. The village close by was the Dhanula Gaon. This place was strewn with rocks and boulders and it was clear that it was the channel of some seasonal stream. The rocks and stones were collected from here for building material.

We were able to see a causeway here. A Causeway is a part of the main road which is a little depressed and concreted to allow a seasonal stream or a channel of water to flow over it, minimising erosion. A causeway was preferred over a bridge here as it was not possible to build the foundation of the bridge in that very place.

Along the banks of the river and seasonal stream, we found lateral Gabions placed at an angle of 45°. It was so to minimise erosion by the river and also to prolong the life of the gabions.

We were also able to see the convexity and concavities created by the seasonal flow of the river. From the deposits and convexity it was found that the river deposits its materials on the concave side whereas erodes at the convex side.

Spot 3, Baldi River: This is the place where our bus was parked and we were on foot. It was midway between Sahastradhara and Kali Rao. We could see another causeway here. A waterfall was close by. All along the course of the river, Checkdams had been laid. At a distance, we could also see restored mined lands. The vegetation found here was Bottle Brush, Arundineria sp.and Lantana spp.

Continue reading – Part 2, Part 3, Part 4

Author’s Bio

Raghu Ranjan Rai is a Forestry (GIS) post-graduate and is presently a Manager Forestry Operations and GIS in S & P Energy Solutions PLC Ethiopia (SP Group Mumbai). His primary area of interest is GIS mapping and Forestry operations. Contact him at- raghufri09(at)gmail(dot)com