Integrated Reservoir Catchment Management Approach for Restoration of Lakes and Reservoirs

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Integrated Reservoir Catchment Management Approach for Restoration of Lakes and Reservoirs

(A Case Study for Nellegudde Reservoir Catchment, Ramanagaram District, Karnataka, India)

H. Chandrashekar1 K.V. Lokesp Jyothi Roopa3 G.Ranganna4

  1. Selection Grade Lecturer, Dept of Civil Engg, MEI Polytechnic, Rajajinagar, Bangalore560010 India and Research Scholar, Dept of Civil Engg, Dr. Ambedkar Institute of Technology. Bangalore, 560056

  2. Professor, Dept. of Civil Engg. Dr. Ambedkar Institute of Technology, Bangalore 560056.India

3 Research Scholar, Dept of Civil Engg, Dr. Ambedkar Institute of Technology. Bangalore, 560056

4. Visiting Professor, CAS in Fluid Mechanics, Bangalore University, Bangalore.560001.India

Abstract:- Water is the basis of life on earth. It is the main component of the environment and an essential element for human life. Water is also fundamental for sustaining a high quality of life and for economic and social development. But the essential resource is under threat. Increasing demand and untreated waste water discharge aggravates the stress on water bodies. It now appears that one of the main factors limiting the future economic and human development will undoubtedly be water.

Lakes and reservoirs are vital parts of fresh water ecosystems of any country. The water quality of a lake is a reflection of the condition of its catchment. The intensive agricultural practices and land use changes due to residential development in the catchment has reduced the inflow into these reservoirs. The lakes and reservoirs, all over the country without exception, are in varying degrees of environmental degradation. The degradation is due to encroachments, eutrophication and siltation. There has been a quantum jump in population during the last century without corresponding expansion of civic facilities resulting in deterioration of lakes and reservoirs, especially in urban and semi-urban areas becoming sinks for the contaminants. The degradation of reservoir and lake catchments due to deforestation, stone quarrying, sand mining, extensive agricultural use, consequent erosion and increased silt flows have vitiated the quality of water stored in the reservoirs.

The study area viz., Nelligudde reservoir catchment has an areal extent of 65 sq.km.It is encompassed by E Longitude 77º20'46" 77º24'33" and N Latitude 12º46'38" 12º57'16". The

paper discusses the integrated catchment studies for better management of reservoir. The physico-chemical and bacteriological analyses of surface and ground water samples in the reservoir and its catchment reveals that water is polluted at certain locations. Water samples were analyzed for irrigation requirements and USSL diagram, Piper trilinear diagram were plotted for classification of water samples and spatial distribution of water quality parameters is carried out using GIS Arc-Info software. Remote sensing data are used for mapping land use and land cover, physical and chemical analyses of soil samples in the catchment area reveals low fertility index in certain locations, Morphometric analyses were carried out for the entire catchment to determine the linear, areal and relief aspects of the catchment. Double- ring infiltrometer is used for field infiltration measurements. Evapotranspiration studies were carried out using Penmen-Monteth method, soil erosion potential zone mapping is done using Universal Soil Loss Equation (USLE)

which shows severe erosion at certain locations in the catchment area. Estimation of runoff is carried out using SCS-Curve number method using GIS. The Integrated Reservoir Management approach will be an effective tool for sustainable management of lakes and reservoirs. The paper also discusses various management plans for effective management of reservoirs through integrated reservoir catchment management approach

Keywords:- Reservoir catchment, Water and soil quality, Soil erosion, Remote sensing and GIS

INTRODUCTION

Many of the present cities, earlier emerged as settlements, along water bodies. The relation between settlements and water is unique and important. The paradigm here is water and is considered a source, which sustains life, nurtures occupations and supports religious beliefs. The water bodies in an urban set up include the rivers, streams, nallahs, lakes, tanks, wells, etc.

Lakes are vital parts of fresh water ecosystems of any country. A fresh water lake when maintained free from pollution can offer many beneficial uses in an urban area. Urban lakes more commonly act as thermal cooling, reaction centres and de-stressing points in the highly-stressed urban life. Nowadays due to pressure from activities like urbanization, industrialization, as well as the asthetical beauty of the water body, the commercial value of the surrounding area is improved. Lakes provide life to various forms of aqui flora and fauna livelihood for fishermen community, food for the local populace, pollution sink, ground water recharge leading to rise in the water table and as flood mitigators. The urban population can free themselves from the polluted urban air and find solace in the cool air by the lake side and relax in recreational activities such as swimming, boating, fishing and strolling along the lake shores.

The ill-effects of neglecting catchment management have caused urban ecological imbalance, pollution, unhygienic conditions, and floods during rains. The trends of development and increased land demands have caused encroachment of

tank beds, sewage disposal into tanks and nallahs. As a result of increased population growth, intensified use of surface waters exploitation of adjoining lands and properties, and other human pressures, inland lakes increasingly are being threatened.

Restoration means returning of an ecosystem to a close approxiamation of its condition prior to disturbance. This ensures that the ecosystem structure and function are recreated or restored, and that natural dynamic ecosystem processes operate effectively again. The physical, chemical and biological integrity of surface water is achieved by- correcting nonpoint source pollution problems and restoration of all types of habitats with priority to the habitats of endangered species. The most wide spread problems facing lakes in Bangalore are sewage from domestic sector, effluents from industrial sector (point sources), and agricultural nonpoint runoff of silt and associated nutrients and pesticides. This has led to eutrophication, due to excessive inputs of nutrients and organic matter. Hydrologic and physical changes and siltation from catchment activities have resulted in special decline. Lakes are sinks for incoming contaminants that recycle and maintain the impaired conditions. There is an urgent need to take up the restoration of lakes.

Lake revival/rejuvenation/restoration is a much talked about subject in the recent times. Lakes are being destroyed by putting the lake land for different uses in its entirety and the peripheral area encroached upon or the inlet valleys changed/diverted/destroyed.In case the lake land is untouched it is used as a dumping yard for the solid wastes/waste water (sewage, sullage)/effluent from the urban developments in the catchments of the water body.

The above factors hassled to either loss of the lake in its entirety or reduction in the area of the water body or the lake being deprived of aquatic life and choked with aquatic weeds leading to depletion of dissolved oxygen and release of obnoxious gases due to anaerobic reaction in the lake water. Mosquitoes breedin leads to various vector diseases on the surrounding areas of the lake.

Due to inadequate infrastructure facilities for waste disposal in the urban areas the urban lakes get polluted due to there natural topography and as collection points for the waste from the haphazard urban settlements. As a result of this and a number of other compounding factors most of the urban lakes are getting degraded beyond the point of recovery. Encroachments, accumulation of silt, weed infestation, discharge of domestic sewage, industrial effluents are the main causes for degradations of these lakes. Declining water quality, nuisance algae blooms, excessive weed growth, deteriorating fisheries, sediment infilling, eutrophication, contamination, bund erosion, water-use conflicts, impaired scenic qualities and upward appreciation of property values around the lake due to rapid urbanization are common problems being experienced by lake overseers as a result of human activities. These and other critical problems are avoidable. The lakes are prone to the causes of deterioration and degradation.

STUDY AREA

The Nellegudde reservoir catchment and its command with a total extent of 65 Sq. Km is located adjacent to the eastern boundary of the Manchanabele reservoir. About 2 Km SE of the Nelligudde tank is the Bidadi township. The area is bound between E Longitude 77 º20 46 77º 2433 and N Latitude 12º 46 38 12º 57 16 covered in Survey of India topographic map No 57H/5 of 1:50,000 scale. The subject area forms a part of semi-arid tract in the agro climatic environs of East Dry Zone of Karnataka.

Fig 1 Satellite image of Nelligudde catchment and command area

Studies on Geology and Geomorphology of the study area

The Nelligudde tank catchment and its command area is covered over to a large extent by the Younger Gneissic complex. The hill range of the Closepet Granite marks the western boundary of the area. Towards NE part, the younger granites attains the form of isolated hills. The gneissic rocks which are fresh and massive are on the surface exposed intermittently. They are more seen as sheet rocks, stoney wastes and rocky knobs. The gneissic rocks are weathered to shallow depth. The mineral foliation of the gneissic rocks is North-North Westerly. They are dipping easterly at varying angles between 70º and 85º. Dip joints are predominant. Pegmatite and quartz veins are common in the gneissic formations. The contrast between gneissic suite and granite belt in the west is marked by abrupt high rise hills. A major part of the catchment and the command area of Nelligudde tank catchment and its command forms a pediplain terrain with shallow depth of weathering of gneissic rocks.The land use and land cover map is shown in Fig 2.The drainage map is shown in Fig 3.

Fig 2. Land Use and land Cover Map of Byramangala tank Catchment

and Command area.

Fig 3. Drainage Map of Byramangala catchment area.

METHODOLOGY

The physico-chemical and bacteriological analyses of surface and ground water samples in the tank and itscatchment reveals that water is polluted at certain locations. Water samples were analyzed for irrigation requirements and USSL diagram and Piper trilinear diagram were plotted for classification of water samples and spatial distribution of water quality parameters is carried out using GIS Arc-Info software. Remote sensing data were used for mapping land use and land cover. Physical and chemical analyses of soil samples in the catchment area reveal low fertility index in certain locations, Morphometric analyses were carried out for the entire catchment to determine the linear, areal and relief aspects of the

catchment. Double- ring infiltrometer was used for field infiltration measurements. Evapotranspiration studies were carried out using Penmen-Monteth method. Soil erosion potential zone mapping is done using Universal Soil Loss Equation (USLE) which shows severe erosion at certain locations in the catchment area. Estimation of runoff is carried out using SCS-Curve number method using GIS.

MORPHOMETRIC CHARACTERISTICS OF THE CATCHMENT AREA

The morphometric analysis of drainage basin and its stream channel system can better be achived through the measurements of linear, areal relief aspects of the channel network and contributing ground slopes.Drainage network map and slope maps were prepared using Survey of India (SoI) toposheets on 1:50,000 scale. The various morphometric parameters are presented in Tables1 and 2.

Table 1.Catchment morphometric characteristics

Sl No

Catchment Parameters

Units

Values

1

Catchment Area (A)

Sq.km

66.64

2

Perimeter of the Catchment (P)

km

40.30

3

Catchment Stream Highest Order

4

4

Maximum Length of catchment

km

16.30

5

Maximum width of Catchment

km

7.40

6

Cumulative Stream segment

146

7

Cumulative stream length

Km

104.71

9

Drainage density

km/Sq.km

1.57

8

Length of overland flow

km/ Sq.km

0.785

10

Constant of channel maintenance

Sq.km/km

0.46

11

Stream frequency

No/Sq.km

2.19

12

Bifurcation ratio

4.58

13

Texture Ratio(Tr)

3.622

14

Drainage Texture (T)

3.438

15

Length ratio

1.86

16

Form factor

0.45

17

Shape factor

3.99

18

Circularity ratio

0.72

19

Elongation ratio

0.56

20

Compactness coefficient

1.39

21

Total Catchment relief

Km

0.13

22

Relative Relief

0.003

23

Ruggedness Number

0.29

24

Gradient Ratio (Rg)

0.0079

Table2.Drainage characteristics of the catchment

Stream order

1

2

3

4

No. of Segments Nu

105

35

4

2

Total Length (Km) Lu

68.72

19.28

7.46

9.91

Bifurcation ratio (Rb)

3

8.72

2

Mean Length (Km)Msm

0.65

0.55

1.87

4.86

Cumulative no on streams

Nu

105

140

144

146

Stream Length Ratio RL

1.18

0.3

0.38

Drainage Density (Km/Sq.km)

Dd

1.57

The elongation ratio of the catchment is 0.56 which is associated with strong relief and steep grond slopes. The length of overland flow is 0.785 km/km2 which indicates surface runoff entering the stream will be quicker. The value of drainage density is 0.875which indicates the catchment area is coarse textured. The value of constant of channel maintenance is 0.46 km2/km which confirms the presence of structurally controlled stream system within the catchment.

WATER AND SOIL QUALITY ASPECTS.

Ground water samples were collected from the catchment and command areas of the tank and surface water were collected from the lakes and the reservoir durning April 2011,August2011 and January 2012. Physico-chemical and biological analysis was carried out for the water samples collected from various locations using standard procedures recommended by APHA-1994. The results can be used for classifying water for irrigation requirements and drinking water purposes.

The suitability of ground water for irrigation purposes depends upon its mineral constituents.The general criteria for judging the quality are (i)Total salt concentration as measured by electrical cponductivity (ii)Relative proportion of sodium to other principal cations as expressed by SAR,(iii) Soluble sodium percentage.(iv)Residual sodium carbonate and

(v) Residual sodium bi carbonate.

Wilcox (1995) classified groundwater for irrigation purposes based on percent sodium and electrical conductivity.Eaton(1950) recommended the concentration of residual sodium carbonate to determine the suitability of water for irrigation purposes. The US Salinity Laboratory of Department of Agriculture adopted certain techniqes based on which the suitability of water for agriculture is explained.

%Na = (Na+ X 100/ (Ca+2+ Mg+2 +Na++K+)

where the quantities of Ca, Mg, Na and K are expressed in milliequivalents per litre(epm).

The classification of water samples with respect to soluble sodium percent is shown in Table 3. In water having

high concentrations of bicarbonate,there is a tendency for calcium and magnesium to precipitate as water as the soil becomes more concentrated. As a result, the relative proportion of sodium in the water is increased in the form of sodium carbonate. RSC is calculated using

-2 +2 +2

-2 +2 +2

RSC= ( HCO3- + CO3 ) (Ca +Mg )

where all the ions are expressed in epm

According to the US Department of Agriculture, water having more than 2.5epm of RSC is not suitable for irrigation purpose. RSC classification of Water samples of the study area is presented in the Table-4

A better measure of the sodium hazard for irrigation water is sodium adsorption ratio( SAR) which is used to express reactions with the soil. SAR is computed as

SAR= Na+/[ (Ca+2+Mg+2)/2]½

Where all ionic concentrations are expressed in epm

The classification of water samples from the study area with respect to SAR is presented in Table 5. The total concentration of soluble salts (salinity hazard) in irrigation water can be expressed in terms of specific conductance. Classification of water based on salinity hazard is presented in Table 6.

Table 3.Soluble sodium percentage.

Sodium%

Water class

Percentage of Water samples

< 20

Excellent

6.3%

20-40

Good

56.9%

40-60

Permissible

36.8%

>60

Not suitable

NIl

Table 4: Classification of water based on RSC(Residual sodium carbonate)

RSC(epm)

Remarks on water quality

Water samples

<1.25

Good

All the samples belongs to this category

1.25-2.5

Moderate

Nil

>2.5

Unsuitable

Nil

The Physical and chemical analysis of soil samples were carried out at 15 locations as shown in Table9.The chemical analysis of soil samples reveals that soil is deficient in Zn at various locations and having low percentage carbon and available phosphorous.

Table 5: Classification of water for sodium hazard based on USSL Classification

Sodium Hazard class

SAR

Remarks on water quality

Water samples

S1

10

Excellent

Range 1.2 to 4.21 All water samples belongs to this category

S2

10-18

Good

NIL

S3

18-26

Moderate

NIL

S4

>26

Unsuitable

NIL

Table6: Classification of water for salinity hazard

Salinity hazard class

EC

(micro- mohs/cm)

Remark on water quality

Water samples

C1

100- 250

Excellent

NIL

C2

250-750

Good

NIL

C3

750- 2250

Moderately good

873-2198

41 Samples

(97.6%)

C4

2250-6000

Unsuitable

2545

4 samples

(2.4%)

C5

>6000

Highly Unsuitable

NIL

Fig 4 Spatial distribution of TDS in the ground water samples of the tank catchment and command area.

FIELD INFILTRATION MEASUREMENTS

Infiltration characteristics of soil are very important for scientists, engineers and planners. Hydrologists mostly need infiltration data for the estimation of peak rates and volumes of runoff in the planning of dams, culverts and bridges etc. It is also useful for minimizing the erosional hazards. Most important use of infiltration is to the agriculturists and ecologists who are concerned with the availability of soil moisture in the root zone of crops and plants. Hortons equation is used to characterize the infiltration rate in the catchment area of the present study. Double Ring Infiltrometer is used for infiltration measurements. The Hortons equation is as shown below.

fp=fc+(fo-fc)e-kt

where fo is the infiltration rate at the beginning of the storm, fc is the ultimate or final infiltration capacity attained when the soil profile becomes saturated, fp is the infiltration capacity at timet and k is an empirical constant. Horton suggested the above equation for separating rainfall into rainfall excess and infiltration. This equation is applicable only when the rainfall rate exceeds fp. The constant k depends upon both the basin and rainfall characteristics; fo depends upon initial moisture condition of the basin and fc varies depending upon the season.

Table 7 Field infiltration studies

Sl no

Location

Horton's equation

1

Doddaaladamara

F = 8.28+76.709 e -17.762

2

Banandur

F = 7.80 +9.846 e -8.014

3

Chunchanaguppe

F = 6.32 +5.93 e -7.7486t

4

Dodderi

F = 0.75 + 4.255e -6.8182t

Fig 5 Infiltration Rate curve for Doddaaladamara

Table 8 Water quality based on irrigation water requirements in the catchment and command area.

Chlorides meq/l

Sample no

Sodium Adsorption Ratio

Ca+Mg meq/l

Soluble sodium percentage (SSP) %

Magnesium Hazard meq/l

Residual Sodium carbonate RSC in meq/l

Permeability Index

Kelleys Ratio

N-W1

2.9094

14.696

34.9231

0.23789

5.8930

-1.553

50.9768

0.53664

N-W2

1.7746

11.3024

27.1799

0.25255

3.107

-1.057

47.8026

0.37325

N-W3

2.8607

11.7502

37.1112

0.22752

5.594

-1.2012

54.4946

0.59011

N-W4

2.9846

12.6715

37.2198

0.24279

5.928

-0.9937

54.1505

0.59286

N-W5

2.0578

10.3269

31.1673

0.32256

4.245

-1.2977

51.1959

0.4528

N-W6

2.0423

12.4621

29.0317

0.3802

5.3175

-2.4551

47.0463

0.40908

N-W7

2.4184

2.3606

52.6749

0.4356

1.7882

0.011

83.5494

1.11305

N-W8

2.1955

3.3065

46.056

0.50501

2.0452

-0.004

75.704

0.85377

N-W9

2.1944

3.6127

44.9451

0.46813

2.4119

-0.0086

73.8761

0.81637

N-W10

2.2495

14.1801

29.6971

0.39227

6.327

-2.1245

46.9113

0.42242

N-W11

1.9694

15.4173

26.1807

0.42098

6.519

-3.6253

42.6228

0.35466

N-W12

2.1622

8.421

34.5306

0.3994

4.47

-0.421

56.5674

0.52743

N-W13

2.8759

6.7959

43.8771

0.51915

4.276

-0.0074

65.4894

0.7818

Table9 Results of chemical analysis of soil samples in the Study area.

Sample no

Name of the village

pH

EC

mmh os/c m

Organic Carbon

Availabl e Phosphor us (P) Kg/acre

Av. Potash (K)

Kg/acr e

Available Micro nutrients

Zn ppm

Cu ppm

Mn ppm

Fe ppm

%

N-S1

Chunchanakuppe

6.1

0.02

0.47 L

8 L

146 H

1.62 S

1.9 S

42 S

43.4 S

N-S2

Doddamaranahalli

5.7

0.01

0.22 L

4 L

64 M

0.85 D

2.1 S

34 S

46.3 S

N-S3

Chikkanahalli

7.9

0.08

0.38 L

5 L

92 M

0.97 D

2.2 S

35.1S

39.9 S

N-S4

Dodderi

6.2

0.05

0.52 L

8L

86M

0.65D

1.98S

62.3S

56.2S

N-S5

Ganakallu

6.8

0.02

0.64M

11M

112M

0.98D

2.76S

56.5S

60.4S

N-S6

Kakaramahalli

6.3

0.03

0.33L

9L

108M

1.14S

2.98S

33.7S

43.2S

N-S7

Kenchanakuppe

7.1

0.07

0.59M

6L

75M

0.73D

1.15S

42.1S

55.3S

N-S8

Gollahalli

6.1

0.12

0.48L

10M

69M

0.98D

2.05S

45.1S

59.4S

N-S9

Timmapanapalya

6.9

0.09

0.37L

7L

89M

1.12S

1.99S

29.2S

38.6S

N-S10

Settigoudanadoddi

7.2

0.14

0.69M

12M

102M

1.56S

1.79S

25.1S

32.1SS

N-S11

Sarasegoudanadoddi

7.0

0.09

0.42L

9L

72M

0.68D

1.49S

58.1S

44.6S

N-S12

Muddapurakarenahal li

6.5

0.11

0.39L

13M

138H

1.99S

2.36S

47.5S

52.7S

N-S13

Bannikuppe

7.3

0.03

0.51M

14M

121H

2.13S

1.56S

49.5S

55.8S

N-S14

Banandur

6.2

0.04

0.72M

11M

101M

1.48S

1.62S

39.5S

40.3S

N-S15

Doddaaladamara

7.9

0.06

0.49L

12M

87M

0.98D

1.49S

27.9S

39.1S

H-High, L-Low, M-Medium, S-Sufficient, D-Difficient

EVAPOTRANSPIRATION MEASUREMENT

Evapotranspiration (ET) includes water that is needed for both evaporation and transpiration.ET is defined by the US Geological Survey as the water lost to the atmosphere from the ground surface, evaporation from the capillary fringe of the ground water table, and the transpiration of groundwater by plants whose roots tap the capillary fringe of the groundwatertable. Evapotranspiration is considered to be one of the key elements in the water cycle that needs to be quantified to achieve better water management. In the present study Penman-Monteith method FAO-56 is used for the computation of Reference evapotranspiration.The max and minimum values of monthly evapotranspiration for 3 locations for past 5years is shown in Table 10. The FAO-56 Penman-Monteith Equation for computation of reference evapotranspiration is shown below.

Table 10 Monthly ETOvalues in mm/month for various

<>locations

Location

Chikanahalli

Dodderi

Banandur

Year

Min

Max

Min

Max

Min

Max

2008

82.05

126.24

83.1

127.75

83.19

129.25

2009

72.18

121.32

73.79

120.27

75.92

121.54

2010

68.28

126.51

68.41

127.96

68.69

127.43

2011

85.45

125.19

84.29

125.23

84.66

125.41

2012

88.24

129.56

87.19

126.21

87.96

125.88

(All units are in mm)

SOIL EROSION STUDIES

The soil loss in the Byramangala catchment area is estimated using Universal Soil Loss Equation (USLE).The inputs for the model such as soilmap, landuse landcover map and slope map were derived from satellite images of IRS PAN+ LISS III after suitable ground truth studies.The slope map is prepared from SRTM data. Following formula is used in computation of Soil loss.

A=RKLSCP

where, A is the computed soil loss in tons/hectare/year, R is the rainfall factor which is also called as erosion index, EI which is taken from Isopleths for the present study it is taken as 250, K is the soil erodibility factor which depends on the soil type. For the present study the weighted average value is calculated as 0.31.Lis the slope length factor and S is the slope steepness factor and the value of LS for the present study is calculated using Arc-Info GIS software. C is the crop management factor which is derived using land use and land cover map. P is the conservation practice factor. Since the study area comprises of field bunds the conservation factor is taken as unity.The above map layers were overlayed using Arc-Info GIS software and soil loss is computed in the catchment The soil loss in the catchment varies between 0 to 50 tonns per hectare per year. The soil erosion map is shown as Fig-6.

RUNOFF ESTIMATION USING SCS-CN METHOD

The SCS Curve Number method (USDA, 1977) is the most enduring method for estimating the volumes of direct,i.e., surface runoff from ungauged small catchments. In the present study SCS Curve Number method is used to estimate the surface runoff. The weighted curve number is derived by superimposing Hydraulic soil Group (HSG) classification map and land use and land cover map using GIS Arc-Info Software. The weighted Curve number of 71 obtained for the catchment is used to estimate the Runoff using the following equation.

where Q is the runoff in mm, P is the Rainfall in mm and S is the maxium soil water retention parameter and CN is the weighted curve number for the Catchment. The seasonal runoff is estimated using the seasonal rainfall data. For monsoon rainfall of 577mm for the year 2012 the estimated runoff is 102.1mm.

Fig 6 Soil erosion map of Nelligudde tank catchment.

CONCLUSIONS

The results of the morphometric analysis help in priotorising the sub-catchments. The morphometric characters derived will help better management of the reservoir catchment which further helps in the management of the reservoir. The results of analysis of water and Soil samples at various locations of catchment area revel that

water is not suitable for irrigation and potable purpose and soil samples at various locations are deficient of Zinc, low organic carbon and low phosphorous, hence precautions should be taken to identify pollution potential zones and take preventative measures. From the results of field infiltration studies it is concluded that soils of the study area have medium to high infiltration capacities. It is observed from the computations of ETO by Penman-Monteith method for 5 years duration is between 69.78mm/month to 128.86 mm/month. From soil erosion studies it is concluded that very severe erosion is observed in the catchment area hence proper measures are to be taken to prevent further soil erosion, which also helps in reduction of sediment upload into the reservoir. Thus SCS-CN method is an effective tool for estimating the runoff into the reservoir and also helps to analyse the reasons for reduced inflow into the reservoirs due to the various land use changes. The remote sensing and GIS is an effective tool for management of tank catchment which in turn helps in the governance of reservoir.

ACKNOWLEDGEMENTS

The authors wish to place on record their thanks to Management, Principal and Head of the Department of Civil Engineering of MEI Polytechnic, Rajajinagar, Bangalore, India and Management, Principal and Head of the Department of Civil Engineering of Dr.Ambedkar Institute of Technology, Malatahalli, Bangalore, India for their help and encouragement during the present research work and preparation of this paper.

REFERENCES

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