water balance study ppt

Download WATER BALANCE STUDY ppt

Post on 09-Jan-2017

93 views

Category:

Documents

5 download

Embed Size (px)

TRANSCRIPT

WATER BALANCE STUDY USING GEC-97 METHODOLOGY

USING GEC-97 methodology

WATER BALANCE STUDY Hydrogeological Map of India

Background First time in 1979, the ground water resources were estimated using a methodology recommended by, 'Committee on Over-exploitation of Ground Water Resources constituted by Agriculture Refinance and Development Corporation (ARDC).

In 1984, the methodology was modified by a committee known as 'Ground Water Resources Estimation Committee (GEC)'. Upon completion of the assessment of ground water resources of the country, GEC-1984 was used.

Again in 1997, the Ground Water Estimation Committee reviewed the previous studies and work done in various states and suggested a modified methodology in 1997 (GEC97) for computation of ground water resources.

To get a more appropriate methodology for ground water resources estimation for hard rock terrain, which will supplement the GEC-1997, Ministry of Water Resources, Govt. of India, constituted a committee (and revised GEC-97) on 03.09.2001.

Source : Dynamics GW Resource 2011( CGWB, 2014) , Report on the Hard Rock Ground Water Estimation (CGWB)

EEEEDirect RechargeIndirect RechargeLocalized RechargeEEE = Evapotranspiration Schematic representation of Recharge

Salient features of their recommendations are given below Hard rock areas the assessment is made with respect to watershed unit.

The total geographical area is divided into subareas such as hilly regions (slope > 20%), saline groundwater areas, canal command areas and non-command areas, and assessment is made separately for all these subareas

During the non-monsoon period recharge from rainfall and other sources is based on the Rainfall Infiltration Factor and other prescribed norms

Norms for return flow from groundwater and surface water irrigation are revised taking into account the source of water (groundwater/surface water), type of crop (paddy/non-paddy) and depth of groundwater level

There should be at least 3 spatially well-distributed observation wells in the unit, or one observation well per 100 sq. km. whichever is more

Categorization of assessment unit is to be governed by long term water trends besides the stage of developmentSource: GROUNDWATER ASSESSMENT METHODOLOGY - C. P. Kumar Scientist F, National Institute of Hydrology, Roorkee, Report on the Hard Rock Ground Water Estimation, By CGWB

WATER BALANCE EQUATION The following equation is a generalized form of water balance equation, which applies to any assessment unit irrespective of it being an administrative unit, a watershed or an aquifer. This water balance equation holds good for any part of the year and for the annual water balance as well.

S= + other /

S =Change in storage in ground water reservoir =Recharge from rainfallother =Recharge from other sourcesB = Base flowall = Ground water draft for all uses = Evapotranspiration losses =Leakage to or from deeper aquifersO / =Net inflow/outflow across the boundary of the assessment unit or S= + other =The net inflow/ outflow from the unit which is the resultant of base flow, evapotranspiration losses, leakage from or to the deeper aquifers, net flow across the boundaries etc

Source -Assessment of Ground Water Resources : A Review of International PracticesRana Chatterjee, Scientist D Ranjan Kumar Ray, Scientist CBUT Why do we study water balance , development and management of groundwater resources?

Methodology The methodology used for estimating the annual replenishable groundwater resources is known as Groundwater resources estimation methodology1997(GEC-1997), involves estimation of annual groundwater recharge from rainfall and other sources including irrigation, water bodies and artificial recharge and determination of present status of groundwater utilization.(Recommended by government of India for all states and Union territories)

Groundwater recharge estimation in GEC-1997 is computed season-wise(i.e. monsoon and non-monsoon season)

Source:- Dynamic groundwater resources of National Capital Territory, Delhi: assessment, development and management options Rana Chatterjee ,B. K. Gupta , S. K. Mohiddin P. N. Singh ,Shashank Shekhar , Rajaram PurohitNON MONSOON SEASONMONSOON SEASON Water level fluctuation method (WLF) and empirical norms are usedFOR RECHARGE ESTIMATION THE FOLLOWING METHODS ARE USED.Empirical norms

Total annual recharge =Recharge in monsoon season (from rainfall + other sources)+ Recharge in non-monsoon season (from rainfall + other sources)Source :- 1) Hydrology and Water Resource Of India by Sharad K. Jain, Puspendra K. Agarwal and Vijay P. Singh2) Dynamic groundwater resources of National Capital Territory, Delhi: assessment, development and management options Rana Chatterjee ,B. K. Gupta , S. K. Mohiddin P. N. Singh ,Shashank Shekhar , Rajaram Purohit Recharge (R) = Sy(dh/dt)(Scalnon et al: 2002; Healy and Cook 2002) where Sy is specific yield, h is water table height and t is time

Considering the heterogeneity of the hydrogeological setup and complexities in the GW flow hydrodynamics, the estimations using GEC-1997 should be followed by micro-level studies before a large scale GW management plan is contemplated.Recharge estimation using GEC-1997 Estimation of recharge involves following steps:1.Work out recharge during monsoon season (July to October) using WLF method----------------------------------- (2)R= h X Sy X A + DGWhere,R= possible recharge, which is gross recharge minus the natural discharges in the area in the monsoon season (hectare metre)H= WLF between pre-monsoon (May) and postmonsoon (November)A= area of computation of recharge (hectare)Sy= specific yieldDG= groundwater draft during monsoon season (hectare metre)Source:- Dynamic groundwater resources of National Capital Territory, Delhi: assessment, development and management options Rana Chatterjee ,B. K. Gupta , S. K. Mohiddin P. N. Singh ,Shashank Shekhar , Rajaram Purohit

2.Segregate the resultant recharge [arrived at Eq. (2)] into recharge from rainfall and recharge from other sources.

Source:- Dynamic groundwater resources of National Capital Territory, Delhi: assessment, development and management options Rana Chatterjee ,B. K. Gupta , S. K. Mohiddin P. N. Singh ,Shashank Shekhar , Rajaram Purohit------------Where,RMrfi = recharge from rainfall during monsoon for the ith particular yearRMc= recharge due to seepage from canals during monsoon for the ith particular yearRMsw =recharge from surface irrigation during monsoon for the ith particular yearRMt =recharge from storage tanks and ponds during monsoon for the ith particular yearRMgw =recharge from groundwater irrigation during monsoon for the ith particular yearRMwc =recharge from water conservation structure during monsoon for the ith particular year

3. Normalize rainfall recharge for estimating recharge corresponding to the normal monsoon rainfall.This was done in order to neutralize the effect of excessive or less than average rainfall on groundwater recharge estimation of a particular year.Source:- Dynamic groundwater resources of National Capital Territory, Delhi: assessment, development and management options Rana Chatterjee ,B. K. Gupta , S. K. Mohiddin P. N. Singh ,Shashank Shekhar , Rajaram Purohit------------WhereRMrf (normal)= normal monsoon rainfall rechargeRMrfi =monsoon rainfall recharge for the ith particular yearr (normal)= normal monsoon rainfallri =monsoon rainfall of the ith particularyear

Source:- Dynamic groundwater resources of National Capital Territory, Delhi: assessment, development and management options Rana Chatterjee ,B. K. Gupta , S. K. Mohiddin P. N. Singh ,Shashank Shekhar , Rajaram Purohit

4. Compute rainfall recharge using RIFWhere, f is RIF and,----------------A =area of computation of recharge (hectare) and rM normal rainfall in monsoon season (metre)5. Compare the rainfall recharge figure arrived at Eq. (4) [RMrf (WLF)] with rainfall recharge figures using RIF [RMrf (RIF)] for normal monsoon rainfall arrived atEq. (5).PD Difference in WLF & RIF estimate expressed as a percentage of RIF estimateIf,a) if PD is within 20%, RMrf = RMrf (WLF)b) if PD is20%, RMrf = 1.2xRMrf (RIF)-------------------------

Source:- Dynamic groundwater resources of National Capital Territory, Delhi: assessment, development and management options Rana Chatterjee ,B. K. Gupta , S. K. Mohiddin P. N. Singh ,Shashank Shekhar , Rajaram Purohit6. Work out the total normal recharge during monsoon period.

------------------

----------------7. Work out the normal rainfall recharge during non monsoon period (November to June of Next year) using RIF.8. Compute recharge from other sources during non monsoon season.9. Work out total recharge during non-monsoon season.

----------

----------

Source:- Dynamic groundwater resources of National Capital Territory, Delhi: assessment, development and management options Rana Chatterjee ,B. K. Gupta , S. K. Mohiddin P. N. Singh ,Shashank Shekhar , Rajaram Purohit10. Annual replenishable groundwater resource is the sum total of monsoon and non-monsoon recharg