SEDIMENTATION ANALYSIS OF THATIPUDI RESERVOIR USING REMOTE SENSING & GEOGRAPHIC INFORMATION SYSTEM

ByShahera Begum (10331A0149) P.V.Srivardhan (10331A0142)

G.Rajya Lakshmi (10331A0121) K.Gana Chaitanya (10331A0123)

B.Jhansi (10331A106)Under the Guidance of

Mr. A. Vara Prasad M.Tech (RS & GIS)Assistant Professor

Objectives

• To analyze the sedimentation rate of Thatipudi Reservoir basing on field survey

• To analyze the Land use and Land cover of study area for a period of 30 years using remote sensing.

• To analyze the drainage pattern of the study area using Geographical Information System.

Description of Study area• Thatipudi Reservoir Project was constructed across

Gosthani River.• Location: Gantyada mandal, Vizianagaram disrict.• Latitude: North 18.1699 , Longitude: East 83.1975• Purpose: To irrigate a total ayacut of 15,378acres

(62.23sqkm).• Head work: Earthen and Gravity: 585m long.• Full reservoir level: 90.52m• Gross storage capacity: 94.164MCM.• Live storage capacity: 88.04MCM.

Thatipudi reservoir along with its watershed and drainage pattern

Methodologies

Topographical Satellite Field Work

Contour Toposheet Analysis

Base Map Creation

Selection of Study Area

Procurement of Satellite Images

Re-sampling of Satellite Images

Supervised Classification

Geo Referencing

Data Processing

Actual water spread and volume estimation

Comparison & Analysis

Classified Image

Sample signature

Recoding

Drainage

DEM

Data collection

Results & Recommendations

Data collection• Data was collected from irrigation department which constitutes of details

related to precipitation, inflow, outflow, capacity of reservoir for the past 30 years i.e., from 1980-2013.

• Area elevation curve of Thatipudi reservoir is also collected.• Satellite images from National Remote Sensing Centre (NRSC) and earth

explorer were also taken for land use and land cover analysis. The dates for which the satellite images were classified are:

From Earth Explorer website-In the year 1973,October, year 1975 December, year 1977 February

From NRSC-In the year 1988, October, year 1990, February From Bhuvan -In the year 2009, October, year 2011, December• Water depths at various locations in the reservoir were measured to

compute the amount of sediment upto year 2014.

1.Estimation of volume of sediment based on field survey conducted on 28th February, 2014

Field survey – • Depth of water column at various locations were determined

in the reservoir area.• The average value of depth of water column was taken and

depth of sediment deposited on the reservoir bed was calculated with respect to bed level.

• Amount of sedimentation was calculated using prismoidal formula.

Water depth of reservoir

Average water column is 52.387 ftDepth of sediment deposited is given by Level upto which sediment is deposited - Bed level = (Reservoir level - Average water column)-Bed level = (292 - 52.387) - 220 =19.613 ft

Sediment calculation

Prismoidal formula is given by: V=H(A1+A2+√A1*A2) / 3WhereV=volume of sediment deposited H=Difference in depth between two successive depth contoursA1=Cross section area within the outer depth under considerationA2= Cross section area within the inner depth under consideration

The total volume of sediment deposited is 51.84 MMCF

Results obtained from field survey:Volume of sediment obtained yearly basing on rainfall data

Graph showing sediment deposition and annual rainfall versus years

2.By creating 3D-DEM:• Surface areas from different time periods are obtained based on different images

available.• Contours are generated based on those areas and Reservoir DEM is created.• Similarly another DEM is created based on the water level depths obtained from

field survey data.• In Arc Scene, those two DEMs are overlapped and the sediment volume is

calculated , i.e., the volume under sediment plane.• The approximate volume of sediment is found to be 63MMCF

Result obtained:

Reservoir side viewReservoir 3D view

Reservoir with sediment plane 1 Reservoir with sediment plane 2

The estimated sediment volume is found to be 63MMCF by 2014.

3.Land use and land cover analysis

Image classification is done to know the land use pattern.• It is mainly done in 3 steps:

1. Geo-referencing: The available satellite image is geo-referenced to an already available reference image like a topo-sheet2. Subset: The geo-referenced image is then clipped to the required watershed area3. Supervised classification: The clipped image is then classified on the basis of supervised classification

• The change in cover for different years is analyzed and the possible sedimentation causes are determined.

Results of supervised classification1973

1975

1977

1988

1990

2009

2011

Comparizon of percentage area of each class

The table enlisted above for various classes depicting the areal spread clearly shows that major part of the water shed is vegetation. In the year 1988 and 1990 there was a sudden decrease in vegetative cover which might be due to deforestation. In these years area under agricultural increased tremendously.

Percentage area under each class versus years

4.Drainage pattern determination

Drainage pattern in the year 2005 and 2011

Discussions• The amount of sedimentation obtained using theoretical

formula was 51.84 MCft where as that obtained by using Arc GIS was around 63 MCft. If better survey methods would have been used then the values might have been more comparable.

• Basing on rainfall data the estimation of sediment deposited yearly plotted in the form of graph shows a deviation in the year 1990 which is very high compared to other years.

• In the year 1990 the vegetation area suddenly reduced which might be the possible reason for increase in sediment deposition.

Thank you