Vol. 04, Issue 05, May 2019 Available Online: www.ajeee.co.in/index.php/AJEEE ESTIMATION OF SEDIMENT YIELD FOR SUBBASIN PRIORITIZATION: A CASE STUDY
OF TAVARJA LAKE CATCHMENT IN GODAVARI DRAINAGE BASIN OF MAHARASHTRA, INDIA
Atul M. Jethe1 and Sunil W. Gaikwad2
1C.T.Bora College, Shirur, Dist.Pune-412210.
2Head and Associate Professor, S.P.College,Pune-30.
Abstract - Soil erosion due to rainfall runoff is a global phenomenon. The eroded sediment gets deposited in the lake or reservoirs, eventually reducing the storage capacity. To assess the SYI, it is necessary to prepare slope, LULC, Soil texture, GSY and SDR of the study area.Hence estimation of sediment yield has become one of the important task for researchers, planners, engineers and descision makers.This paper aims to prioritize the sub-basins by estimating sediment Yield Index (SYI) for identification of the cretical areas which need immidiate remedial measures in Tavarja lake catchment of the Godavari river basin in Maharashtra.On the basis of SYI very high priority for conservation planning of sub basins of watershed requires for TLCW 8.8., TLCW 8.13, TLCW 8.14, TLCW 8.16, TLCW8.17 and TLCW 8.24 etc.While sub basins of TLCW 8.7, TLCW 8.11, TLCW 8.19, TLCW 8.20, TLCW 8.32 and TLCW 8.33 requires high priority for conservation planning.
These areas require immidiate attention. Conservation methods are suggested and the location of check dams, gully plugs and cement bunds are proposed after considering SYI of Tavarja lake catchment
Keywords:Sediment Yield Index(SYI),Sediment Delivery Ratio SDR, EIMU’s,GSY, Sub basin prioritization.
1.INTRODUCTION
The soil covering the surface of the earth has taken millions of years to form. Soil is formed at a rate of only 1 inch every 1000 to 1200 years and it takes 3000 to 12000 years to build enough soil to form productive land. This means that, soil is a
‘nonrenewable resource’ and once destroyed it is gone forever.[1]Soil erosion is universilly recognized as a serious global problem that not only threatens sustainable agriculture but also ecosystems ( Jain, Mishra, Surendra and Shah 2010). Soil erosion due to rainfall and runoff is major erosion which contributing to land degradation. The eroded soil moves downstream in the form of sediments. The amount of sediment load passing through the outlet of a watershed is known as sediment yield.(
Bhujan and et.al 2002). The major factors influencing the sediment yield are the land use perticularly, the vegetation, the soil, the slope and the intensity of rainfall. The severity of this problem is more pronounced in semi-arid regions especially where high rainfall intensities of short duration. Susceptibility of soil to eerosion and human mismanagement of land have accelarated soil lossess through
There are several empirical models based on geomorphological parameters that were developed in the past to qualify sediment yield resulting from erosion. In addition, other methods such as Sediment yield resulting from erosion. In addition, other methods such as Sediment yield Index (SYI) developed by Bali and Karle (1977) and Universal Soil Loss Equation (USLE) developed by Wischmeir and Smith, 1978.
Remote seensing and GIS can be used to determine SYI input parameter such as slope, LULC, Soil parameters, Sediment Delivery Ratio (SDR) etc. Soil is considerd as a basic element in cevil engineering fields. Therefore RS and GIS technique can be used to determine the Sediment Yield Ratio.[3][4]
2.OBJECTIVES
1. The main objective of this study is to estimate sediment yield in Tavarja lake catchment using Sediment Yield Index (SYI) method.
2. To suggest the sub basin prioritization using SYI method .
3. THE STUDY AREA
Vol. 04, Issue 05, May 2019 Available Online: www.ajeee.co.in/index.php/AJEEE and can be classified as macro
watershed.It is roughly elongated and bowl shaped and most of its area comes under agricultural land. Study area occupies its pozition in semi-arid track of Maharashtra therefore it exhibits different kind of geomorphological processes.
The Tavarja lake catchment extends between 18˚14’ 00’’N to
18˚24’00’’N latitude and 76˚ 15’00’’ E to 76˚27’00’’E longitude. The study area is located in Latur and Ausa tahsils of Latur district and Osmanabad tahsils of Osmanabad district. Tavarja river basin is one of the sub basin of river Manjara.It covers an area of about 250.52Km2. The location map of the stuudy area is shown in the figure no.1
Fig.no.1. Location map of the study area (Tavarja lake catchment) 4. DATABASE AND METHODOLOGY
The base map of the study area has been prepared from the Survey of India (SOI) toposheets numbers 56 B/3, 56 B/4, 56 B/7 and 56 B/8 having the scale of 1:50000 published in 1972 were cover cover colleted from SOI, Pune and observed that the total study area of the TLC falls in Godavari drainage basin of Maharashtra. Toposheets were used not only to deliniate the watershed and micro- watersheds but also for the preparation of the base map containing information about drainage, contours etc. The Google Earth pro images were used to prepare a
Landuse Landcover (LULC) map. Rainfall data for the study period were produced from irrigation department Latur. The other relevant information was obtained from various government sources in the form of maps, reports and ancillary data set.
In order to understand slope characteristics of the watershed slope map was derived from DEM. SYI was computed taking inputs from drainage parameters Land use/cover, slope area to assess sediment yield rate in Tavarja lake catchment. The following flow chart describes the methodology for study.
Vol. 04, Issue 05, May 2019 Available Online: www.ajeee.co.in/index.php/AJEEE Fig No.2. Schematic flow chart for micro-watershed prioritization
5 RESULT AND DISCUSSION 5.1.The SYI
A number of sediment yield models, both empirical and conceptual are in practice to address wide ranging soil and water management problems. The sediment yield index model developed by All india Soil and Land Use Survey ( Department of Agriculture, Government of India) was followed for calculating sediment yield index. The SYI model considering sedimentation as product of erosivity, erodibility and areal extent was conceptualised in the all india soil and
land use survey as early as 1969 and has been in operational use since then to meet the requirements of smaller sub basin hydrologic units within the lake catchment areas.
The SYI model
conceptualizes sediment delivery from a hydrologic unit into a reservoir as a multiplicative function of the potential soil detachment representing the erosivity factor: the trasportability of the detached material ( delivery ratio) and the area of the hyrologic entity. This can be expressed as;
SYI Data sources
SOI toposheets 1:50000
Soil map ASTER
BEM 2012
Rainfall data irrigation dept.
Latur
Watershed boundary & slope
Soil texture
LU/LC
Rainfall erosivity from USLE
method
Assigned Weightage vallues using SYI method
Calculated Delevary rstio ,GSY and obtained SYI values
Sub basin prioritization calculated using SYI
Proposed Conservation measures and planning for sub basin
management
Vol. 04, Issue 05, May 2019 Available Online: www.ajeee.co.in/index.php/AJEEE Sediment Yield= f(Erosivity of soil X delivery ratio X area of hydrologic unit)
Soil erosivity f= ( slope,soil parameters, LULC) SYI =Σ (Ai X Wi X Di ) X 100 i=1 to n Aw
Where SYI = Sediment Yield Index Ai = Area of ith mapping unit
Di = Adjusted delivery ratio assigned to ith mapping unit N= Number of mapping units
Aw = Total area of sub watershed 5.2. Sediment Yield Weightage Value
The sediment yield weightage is a function of climate, physiography, slope, soil, landuse and management practices. The soil erosivity detrminents are the soil and land attributes that have direct or reciprocal bearing on the unit of detached soil material.
The relationship can be expressed as;
Soil erosivity = f (slope, soil parameters,Land Use / Land Cover LULC) The function behaviour of each attributes are as followings
5.2.1. Slope
As the slope becomes steeper, the runoff co-efficient increases, the kinetic energy and carring capecity of the surface flow becomes greater, soil stability and as well as the slope stability decreses and splash erosion increases. Following are the extent of percentage of slope in the Tavarja lake catchment
Table No.1. Percentage of slope in Tavarja Lake catchment
Sr. No. 1 2 3 4 5 Total
Slope in % ˂5 5-10 10-15 15-20 ˃20 ˂5 to ˃20
Km2 50.29 121.32 58.02 16.01 4.86 250.52
Percentage 20.07 48.43 23.16 6.39 1.94 100
Fig. No. 3. Tavarja Lake Catchment- Extent of % slope area 5.2.2. Land use/ Land Cover (LULC)
Land use/ Land cover analysis for Tavarja drainage basin has been performed to provide a LULC inventory of the area. Global Mapper 11.02 software used to identify areas under different land use land cover categories
Vol. 04, Issue 05, May 2019 Available Online: www.ajeee.co.in/index.php/AJEEE Table No.2 . Tavarja Lake Catchment Extent of LU/LC category
Sr. No. 1 2 3 4 5 6 Total
LULC Built-up
Land Barren
Land Vegetation
cover Fallow
Land Agricultural
Land Water body
Km2 8.98 17.64 12.35 38.66 165.27 7.62 250.5
Percentage 3.58 7.04 4.93 15.42 65.92 3.04 100
It revels from that the maximum area about 76.63% i.e. 169.55 km2 of the total area is under agriculture land, forest land 12.35 km2 i.e. 4.93%. settlement 8.98 km2 i.e. 3.58% and water bodies about 3.54km2 i.e. 1.41%. Very high proportion of waste land is confined to the northern part of the study area.
5.2.3.Soil Parameters
Soil texture influencing erodibility include particle size, distribution, organic matter content, infiltration rate and soil permiability is a function of soil texture, coarse fragments, effective soil depth etc. determines the quality of surface flow, soil erodibility is also governed by active surface area of the soil particles.
Fig.No.5. Composite map of Soil erodibility
Vol. 04, Issue 05, May 2019 Available Online: www.ajeee.co.in/index.php/AJEEE 5.3.Erosion Intensity Mapping Units
(EIMU)
Erosion Intensity Mapping Unit (EIMU) (Fig. No. 6.) is an assemblage of land and soil characteristics viz.Pysiography, slope land use and land cover with density, surface condition, soil depth, texture and structure of surface and sub soil color drainage condition, salinity and alkalinity, stoniness and rockiness erosion condition and existing management practices.
In the present study area Sedimnt Yield Index (SYI) is calculated using EIMU as above 25 kg/m2/year is very severe, between 20 to 25 kg/
m2/year is severe, between 15 to 20 kg/
m2/year is very high EIMU value, between 10 to 15 kg/ m2/year is high EIMU value between 5 to 10 kg/ m2/year modewrate value and below 5 kg/ m2/year is low EIMU value.
Fig. No.6. Tavarja Lake Catchment- Erosional Intensity Mapping Unit
5.4.Sediment Delivery Ratio (SDR)
Sediment Delivary Ratio (SDR), refers to the present 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
Fig. No. 7. Tavarja lake catchment- Sediment Delivery Ratio
Vol. 04, Issue 05, May 2019 Available Online: www.ajeee.co.in/index.php/AJEEE 5.5. Gross Sediment Yield (GSY)
The amount of total sediment load passing through the outlet of EIMU catchment or watershed is known as ‘Gross sediment yield’.The major factors influencing the sediment yield are the landuse particularly the vegetation, the soil, slope and intensity of rainfall , it can be calculated as;
GSY= (ΣAi×Wi×Di)
Where ,GSY= Gross Sediment Yield,Ai= Area,Wi= Weightage, Di= Delivery ratio Fig. No. 8. Tavarja Lake Catchment: Gross Sediment Yield
GSY values of the TLC is ranges in between <10 to >40 kg/m2/year. The GSY above 40 kg/m2/year (very high GSY) located in the part of villages at Chata, upper part of Ekurga, Dhakani,Neoli, Gumpawadi, Tavarjkheda, Northern part of Wadji, Borgaon and Southern part of Waswadi.
5.6.Sediment Yield Index of TLC
The Sediment Yield Index of the Tavarja lake catchment is characterised as maximum area that lies under 900
kg/m2/year. It lies in Savargaon, Utti ( Khu.), Utti ( Bk.), Part of Bhada, Andhora, Ekurga, Kalmatha, Borgaon and Naholi etc. villages. Area under SYI 900 to 1500 kg/m2/year lies part of Bhoira, Takali,Wadji, Taqvarjkheda, Kond and Dhakani etc. Area under 1500 to 2100 kg/m2/year lies at Chata, wadji, Waswadi, Neoli and Gumphawadi etc.
while SYI of >2100 kg/m2/year lies part of villages of Gumphawadi, Neoli, Wadji, Kond, Waswadi, Dhakani, Tavarjkheda and Bhoira.
Fig.No.9. Tavarja Lake Catchment: Sediment Yield Index
Vol. 04, Issue 05, May 2019 Available Online: www.ajeee.co.in/index.php/AJEEE 5.7.Prioritization Of Sub Basins Based On Sediment Yield Index (SYI)
SYI provides comparitive erodibility criteria of watersheds in terms of high, medium, low and very low but does not provide absolute silt yield. Prioritization of each sub- watershed has been done on the basis of SYI index, which shall make the basis for selection of area for the treatment of the catchment. The sub watershed details such as area, SYI value and priority assigned for treatment. Location of these sub watershed are given as followings;
Fig.No.10. Tavarja lake catchment: Sub basin watershed prioritization for conservation planning ( Baased on SYI values)
On the basis of SYI values very high priority for conservation planning of sub basin watershed requires for TLCW 8.8 (2487.32 kg/m2/year and 10.5 km2), TLCW 8.13 (2664.09 kg/m2/year and 1.92 km2), TLCW 8.14 (3167.60 kg/m2/year and 4.81km2) ,TLCW 8.16 (3075.48 kg/m2/year and 3.833 km2), TLCW 8.17 (2216.35 kg/m2/year and 11.08 km2), TLCW 8.24 (3984.54 kg/m2/year and 2.45 km2) etc. Sub watershed are required very high priority for conservation planning, while sub basins of TLCW 8.7 (2487.32 kg/m2/year and 6.21 km2) TLCW 8.11 (1607 kg/m2/year and 2.004 km2), TLCW 8.19 ( 1544.89 kg/m2/year and 0.299 km2) , TLCW 8.20 (1669.67 kg/m2/year and 0.939 km2), TLCW 9.32 (1566.15 kg/m2/year and 1.959 km2), TLCW 8.33 ( 1587 kg/m2/year and 0.802 km2), TLCW 9.10 (1505. 95 kg/m2/year and 11.99 km2) TLCW 9.11 (1525.72 kg/m2/year and 1.464 km2) etc. sub basins of the Tavarja lake catchment reqquires high priority for conservation planning on the
6.CONCLUSION
It is concluded that the SYI method was used to calculate soil loss in micro- watershed in the study area. Thematic layers of all parameters for the sediment yield of Tavarja lake catchment were mapped. The highest SYI in the Tavarja lake catchment is above 2100 kg/m2/year. Very high SYI is found in the part of villages at Chata, Upper part of Ekurgaa, Dhakani, Neoli and Gumphawadi, Tavarjkheda, Northern part of Wadji and Borgaon, Southern part of Waswadi etc.moderate SYI i.e. 900 to 1500 kg/m2/year is observed in northern part of Utti (Khu), Bhoira, Chata, Neoli, Dhakani, Tavarjkheda, Kond, Andhora, Waswadi, Bhada and Wadji etc. villages Bopala, part of Chata, Ekurga, Dhakani, Kavthakej, Utti (Khu), Utti (Bk.) and Southern part of Andhora etc. villages lies under the category of low SYI <900 kg/m2/year .
On the basis of SYI very high priority for conservation planning is required for sub basins TLCW 8.8
Vol. 04, Issue 05, May 2019 Available Online: www.ajeee.co.in/index.php/AJEEE (3167.60 Kg/m2/year covered 4.81 Km2
area) TLCW 8.16 (3075. 48 Kg/m2/year covered 3.833 Km2 area) TLCW 8.17 (2216.35 Kg/m2/year covered 11.08 Km2 area) TLCW 8.24 (3984.54 Kg/m2/year covered 2.45 Km2 area) etc.
7. ACKNOWLEDGEMENT
Authors wish to express their heartfelt thanks to Department of Geography, S.P.
College, Pune for providing necessary laboratory facilities for the analysis of soil samples.
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