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Volume: I: Part I: Section: 4: Chapter: 4

4.4.1

Section 4: Chapter 4: Prioritization Considering the massive investment in the watershed development programme, it is important to plan the activities on priority basis for achieving fruitful results, which also facilitate addressing the problematic areas to arrive at suitable solutions. As per ToR we were suppose to classify all the microwatersheds (and sub-watersheds) in 5-6 classes depending on the range of sediment load. This may be called as prioritization. But due to sporadic rainfall the silt sampling was hampered and so calculating the rate of silt load was not possible. Prioritization most of the time can be done through SYI i.e. Sediment Yield Index and data for the same can be obtained through SCIS (Satluj Catchment Information System), so that this procedure can also be followed in future. Formula for this is n Sediment Yield Index (SYI) =∑ (Ai * Wi *DRi) / Aw * 100 i=1 Ai = Area of ith mapping unit (EIMU)

erosion

intensity

Wi = Weightage value of ith mapping unit DRi = Delivery ratio of ith mapping unit Aw = Total area of the watershed n = Number of mapping units.

Erosion intensity Unit Here 1determination of erosion intensity unit is primarily based upon the integrated information on soil

characteristics, physiography, slope and landuse / land cover. But here our study unit being micro-watershed or subcatchment (wherever micro-watershed delineation is not done) and we have considered it as erosion intensity mapping unit (EIMU).

Delivery ratio 2

Delivery ratio based on the type of material, soil erosion, relief length ratio, land cover conditions etc. were assigned to all erosion intensity units depending upon their distance from the nearest stream. 3The delivery ratio is adjudged by the likely delivery of the eroded material into the reservoir. Delivery ratio refers to the percent of the soil material detached from the source area reaching the reservoir through surface flow or travelling through drainage courses. Since the transport phenomenon involves suspension of the soil material and its movement over the land surface of the hydrologic unit, the delivery ratio is governed both by the soil factors affecting the dispersion value of the soils and the watershed attributes determining the flow mechanism. The transport of the suspended material is governed by number of parameters namely shape and size of the watershed, physiography and relief, drainage pattern, drainage density, stream gradient, proximity of the eroded area to the active stream or reservoir and the presence or absence of silt traps within the watershed. As mentioned in above section that we have collected samples at the point just before the stream enters the main river and by 100% sample survey it can be concluded that maximum erosion is along or in

2

1

Environmental Management Plans for Parbati Hydroelectric Power Project –Stage III Kullu, Himachal Pradesh, NEERI.

Environmental Management Plans for Parbati Hydroelectric Power Project –Stage III Kullu, Himachal Pradesh, NEERI. 3 EMP Report of Dibang Multipurpose Project, National Productivity Council, Guwahati.

Comprhensive CAT Plan of Satluj River Basin


Volume: I: Part I: Section: 4: Chapter: 4 proximity to the streams. Considering all the variations due to the kind of secondary and primary data received, availability of the data, we have considered following methodology for prioritization in which all parameters affecting the erosion our considered.

Methodology 4

The resources-based approach is found to be realistic for micro-watershed / subcatchment prioritization since it involves an integrated approach. In the present study, knowledge-based weightage system (Wi as per above formula) has been adopted for the prioritization based on its factors and after vigilantly observation in the field. The basis for assigning weightage to different themes was according to the relative importance of each parameter in the study area. The weightage system adopted here is completely dependent on local terrain and may vary from place to place. The study emphasizes on prioritization of micro-watershed for their development and management on a sustainable basis, based on available natural resources and socio-economic conditions. The various themes, which include drainage density, slope, water capacity, groundwater prospects, wastelands, irrigated area and forest cover, are briefly discussed below. The results of analysis of these parameters are given in Volume II

parameters are then studied and processed for prioritization. iii.

After listing the parameters, weight-ages are given to each parameter and later, ranks are assigned to their relative values. The ranking is done based on the severity because of that parameter for e.g. if parameter ‘A’ has a value high because of which the micro-watershed or sub-catchment is subject to erosion we have ranking its as 1 (first to be treated) whereas if parameter ‘B’ has value low which is good or result into conservation we have marked it as 10 or 5 based on the weightage assigned. In other words, Rank 1 is always allotted to the value which indicates maximum soil degradation or loss of life and/or property. While, rank 5 or 10 is allotted to the value that indicates least soil degradation or loss of life and/or property.

Steps: i.

Based on the field visits and secondary data we selected certain critical parameters.

ii.

Based on the data available, all parameters which affect siltation were listed. These listed

4.4.2

4

Prioritization of sub-watersheds for sustainable development and management of natural resources: An integrated approach using remote sensing, GIS and socioeconomic data S. Srinivasa Vittala1,*, S. Govindaiah2 and H. Honne Gowda3

Comprhensive CAT Plan of Satluj River Basin


Volume: I: Part I: Section: 4: Chapter: 4 iv.

Details of these are provided in table below Sr. No.

v.

4.4.3

Parameters

Weight-age

Ranking scheme

1.

Forest cover density

10

1 to 10

2.

Forest area (%)

10

1 to 10

3.

Wasteland (%)

10

1 to 10

4.

Landslide density

10

1 to 10

5.

Drainage (Km/Km2)

5

1 to 5

6.

Slope %

5

1 to 5

7.

Population density

5

1 to 5

8.

Livestock density

5

1 to 5

density

The detailed ranking process for each parameter is given below: o Forest cover density: Forest cover in India is defined as all lands, more than one hectare in area with a tree canopy density of more than 10%.5 For example, in a MWS, the Forest cover density (FCD) value is high, then it is given rank 10. This is because more FCD value indicates more forest cover which means less soil erosion. o Forest Area (%) The Forest Area (%) is indicative of the percentage of area occupied by forest land out of the total area of the Microwatershed/Sub catchment. When values of Forest area (%) are higher it indicates that the Microwatershed/Sub catchment has higher forested area. As they are good soil binders and reduce soil erosion higher Forest area

(%) is ranked as 10 in ranking scheme.

our

o Wasteland (%) Waste land refers to the area which is not under agricultural use or forest cover in a Microwatershed/Sub catchment. It usually refers to fallow land or residential area in a Microwatershed/Sub catchment. When the values for Wasteland (%) for a Microwatershed/Sub catchment are higher, it indicates denuded or barren land is more. Such areas have no or less soil moisture due to absence of vegetation cover, as a result, there is huge washout of soil during monsoons or snow melt. Hence such areas must be treated urgently by implementing various bioengineering measures. Thus our ranking scheme, areas with higher Wasteland (%) are ranked as 1.

5

India’s Forest and Tree Cover, August 2009:Contribution as a Carbon Sink, Ministry of Environment and Forests, Government of India

Comprhensive CAT Plan of Satluj River Basin


Volume: I: Part I: Section: 4: Chapter: 4 o Landslide density

4.4.4

o Livestock density

The landslide density value for a Microwatershed/Sub catchment indicates the number of landslides per unit area of the Microwatershed/Sub catchment. In a Microwatershed, if the Landslide density value is higher, it indicates frequent occurrences of landslides in the area. The severity of landslides in this area being more, life and property are at stake. Thus it should be treated on an urgent basis. Hence it is ranked as 1 in our ranking scheme.

Livestock (also cattle) refers to one or more domesticated animals raised in an agricultural setting to produce commodities such as food, fiber and labour6. In our project area, Livestock is the collective term used for sheep, goats, cows and oxen. Livestock is generally raised for subsistence or profit. It is a common practice in modern agriculture. Livestock density refers to the number of domesticated animals (sheep, goats, cows and oxen) per unit area of the microwatershed/Sub catchment. If for a microwatershed/Sub catchment the value of Livestock density is more it shows that the number of livestock is more for that area and thus grazing activity is more, hence in order to protect it we need to take urgent measures. Thus if livestock density is high the microwatershed/Sub catchment is ranked as 1.

o Slope (%) The slope (%) for a Microwatershed/Sub catchment has been computed from the map. More slope % for a Microwatershed/Sub catchment indicates that there is severe slope which will result into landslides and landslips during monsoon or snow melt. Severe slope is also associated with less infiltration and more runoff which causes lot of soil degradation. There is a dire need for treating such areas. Hence areas with higher slope (%) are ranked as 1 in our ranking system.

o Drainage density (km/km²) The formula for calculations is:

Drainage density=

Total length of nullahs

in the Microwatershed/

o Population density

Sub catchment (km)

Population density is the human population present per unit area of the Microwatershed/Sub catchment. Microwatersheds/Sub catchments having higher population density indicate that there is dense human population in these areas. Hence, in order to protect life and property it is necessary to treat the Microwatershed/Sub catchment with higher population density first and hence we have ranked it as 1.

Total Area of the Microwatershed/ Sub catchment (km²)

Nullahs refer to all the rivulets and tributaries that are present in the Microwatershed/ Sub catchment.

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Livestock-Wikipedia Comprhensive CAT Plan of Satluj River Basin


Volume: I: Part I: Section: 4: Chapter: 4

vi.

vii.

viii.

These ranks assigned to each micro-watershed/sub catchment are summated. Then we got the grand total of the ranks assigned to each micro-watershed/sub catchment based on the parameters listed above. Later, depending on the values obtained from the summation, another range from 1 to 10 is formulated. Where rank 1 is assigned to the Microwatersheds/Sub catchments which have minimum summated value while rank 10 is assigned to Microwatersheds/Sub catchments which have maximum or highest summated values

4.4.5

Microwatersheds/Sub catchments which have rank 10 is treated last. ix.

Thus this methodology of prioritization helps to decide which Microwatersheds/Sub catchments needs to be treated on an urgent basis.

The results of the prioritization for the various Microwatersheds and Sub catchments have been represented in the Volume II of this report.

Thus the group of Microwatersheds/Sub catchments which have rank 1 is treated on first priority. The priority of treatment would go on decreasing from ranks 1 to 10 where the group of

Comprhensive CAT Plan of Satluj River Basin


4.4_Prioritization