estimation of changes in grounwater storage using recession.pptx

7/27/2019 ESTIMATION OF CHANGES IN GROUNWATER STORAGE USING RECESSION.pptx

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By

Sujay Raghavendra N

12WR10F

ESTIMATION OF CHANGES IN GROUNWATERSTORAGE USING RECESSION CURVE

METHOD



OVERVIEW

OBJECTIVE

INTRODUCTION

STUDY AREA

METHODOLOGY DATA ANALYSIS AND RESULTS

CONCLUSIONS

REFERENCES



OBJECTIVE

The objective of the present study was to quantify the

sub watershed wise changes in ground water storage by using ground water levels.



INTRODUCTION

During dry weather, water stored in the catchment is

removed from soil by ground-water drainage and byevapotranspiration. These processes proceed at different

rates in time and space, and are not readily quantified.

The gradual depletion of discharge during periods with

little or no precipitation constitutes the drainage or

recession rate, graphically presented as the recession curve.



Recession curve, period and segment.



STUDY AREA

The Study area is near to coast of Mangalore located at

mouth of Gurupur River.

Gurpura River Basin has 2000 ha wetland. Our study area is

situated near the mouth of the river with an area about 192

sq km among that two sub catchments taken for the study,where the wetlands are present. Details of the areas are

shown in the table 1.



METHODOLOGY

Establishment of recession equation.



Contd…

Specific yield from recession curve

Estimation of specific yield (Sy) of an area (A) isnecessary in order to quantify the amount of ground water outflow during the Non-monsoon season. In this study anattempt has been made to estimate an average value of

Specific yield by recession curve method for non-monsoonseason.

Where,

d- Total drawdown (m)

t- Time period (days)

α- Recession constant (m/day)



Contd… Changes in groundwater storage

Change in groundwater storage describes the differencein groundwater volume between two time periods. Change

in groundwater storage is calculated by multiplying the

difference in groundwater elevation between two

monitoring periods, by the area overlying the groundwater basin, and the average storativity (specific yield in an

unconfined aquifer)

Where,

ΔG - Change in the Ground water storage (ha-m)

h - Change in Ground Water Fluctuations (m)

A - Area of Influence (ha)

Sy - Specific Yield (%)



DATA ANALYSIS AND RESULTS.



COMPUTATION OF GROUND WATER

STORAGE

Estimation of Specific yield using Recession curve method.



Recession Curve with Exponential Trend line for open well-6



Recession Curve with Exponential Trend line for open well-5



Values of α and Sy computed from

recession curve



Calculation of Depth of fluctuation for

well no: 6 of Catchment A



Calculation of Change in groundwater

storage for well-6 of Catchment A



Calculation of Depth of fluctuation for

well no: 5 of Catchment B



Calculation of Change in groundwater

storage for well-5 of Catchment B



CONCLUSIONS

Very less change of groundwater change is observed,it ranges from 15.94 mm in the month of Nov, 27.35

mm in the month of may for sub catchment-A and

17.02 mm during Nov and 46.01 mm during may for

catchment-B

The GEC, 1997 has recommended the specific yield

range of 2 to 4 per cent for the lateritic provinces. The

currently estimated is being 3.8%.



REFERENCES.

Hall, F.R. (1968). Baseflow recession- “A Review.” water resource. Res., 4(5),973-983.

Healy, R.W. and P.G. Cook. 2002. Using groundwater levels to estimate therecharge. Hydrogeology Journal, 10 (1): 91-109.

Kumar C.P.(1997). “Estimation of natural ground water recharge.” ISH J.Hydraulic Eng., 3(1). 61-74.

Groundwater Resource Estimation Committee (GEC). 1997. Water resourceestimation methodology – 1997. Ministry of Water Resources, Government of India.

Shevenel, L. (1996). “Analysis of Well Hydrographs In A Karst Aqufer: estimation

of specific yields and continuum transmissivities.” J.Hydrology., 174:331-355.

Udayakumar , G.(2008) “Subsurface Barriers For Water Conservation In LateriticFormations” Ph.D. thesis, NITK, Surathkal, India.

Vaishali, S (2009) “Studied on Saltwater Intrusion In The Coastal Dakshina

Kannada District”, Karnataka”, Ph.D. thesis, NITK Surathkal, India.



THANK YOU

estimation of changes in grounwater storage using recession.pptx

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