Report on the Hard Rock Ground Water Estimation

CHAPTER 1

INTRODUCTION

1.1 BACKGROUND

The estimation of ground water resources of the country is being periodically carried out for the purpose of planning of ground water development. First time in 1979, the ground water resources were estimated using a methodology recommended by, 'Committee on Over-exploitation of Ground Water Resources'. 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 using the GEC-1984, it was observed that this methodology needed further modification in the light of enhanced database and experimental studies in the field of hydrogeology. The methodology of GEC-1984 was then revised to the methodology of GEC-1997.

The principle adopted in GEC-1997 methodology, though reasonably valid in an approximately homogenous hydrologic terrain like alluvium may not be applicable for hard rock terrain where the hydrogeological conditions vary widely within small area under prevailing heterogeneous set up. Significantly almost two third of the country is occupied by hard rock terrain.

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 on 03.09.2001.

1.2   COMPOSITION OF THE COMMITTEE

The Committee headed by Chairman, CGWB and drawing members from CGWB, State Ground Water Departments and Academic Institutes, consisted of the following:

1.  Chairman , Central Ground Water Board, Chairman
2.  Member (Survey, Assessment and Monitoring) , Member, Central Ground Water Board,
3.  Dr. Saleem Romani, Member, Regional Director/ Member (SM&L),Central Ground Water Board,
4.  Sh. S.K. Sharma, Member, Regional Director,Central Ground Water Board,
5.  Sh. S.M. Mendhekar, Member, General Manager, National Bank for Agriculture & Rural Development, Mumbai
6.  Prof. B.B. S. Singhal, Member, Formerly Prof., University of Roorkee,Roorkee
7.  Dr. Srikant D. Limaye, Member, Director, Ground Water Institute,Pune
8.  Prof. K. Sridharan, Member, Deptt. of Civil Engineering, Indian Institute of Science,Bangalore
9.  Director , Member, Ground Water Department, Govt. of Andhra Pradesh, Hyderabad
10. Director, Member, Ground Water Surveys & Development Agency, Govt. of Maharashtra, Pune
11. Sh. G.C. Sahu, Member Ex. Engineer In Chief, Water Resources, 1034, Mahanadi Vihar, Post Naya Bazar, Cuttack, Orissa
12. Sh. V.M. Sikka, Member, Regional Director, Central Ground Water Board,
13. Sh. M.B. Raju,* Member, Regional Director, Central Ground Water Board, (* Till Superannuation)
14. Sh. Rana Chatterjee Member Secretary, Scientist 'C' Central Ground Water Board

1.3   TERMS OF REFERENCE

The terms of reference of the Committee are as follows -

(i) To review the scientific studies done in the field of ground water resource assessment in hard rock terrains.
(ii) To re-look into the validity of the recommendations of GEC-1997 regarding the hard rock resource assessment and if found necessary suggest alternate methodology for assessment of ground water resource in hard rock terrain.
(iii) To recommend norm for various parameters applicable for calculation of groundwater resource in hard rock terrain.
(iv) Any other aspect relevant to the terms referred above.

1.4   PROCEEDINGS OF THE COMMITTEE

The Committee held seven meetings, that were also attended by special invitees from various State Government Departments, National Institute of Hydrology and Regional Offices of CGWB. During the course of meetings, several presentations were made on - the case studies undertaken to review the GEC-1997, modifications over the existing methodology and alternate methodologies for ground water resources estimation. Draft reports were prepared by two sub-committees viz., Sub-Committee I comprising - Sh. P.C. Chaturvedi, Member (SAM), CGWB, Dr. Saleem Romani, Member (SML), CGWB and Sh. V.M. Sikka, Regional Director, CGWB and Sub-committee II comprising Dr. B.B.S. Singhal, formerly Professor of University of Roorkee. Sh. Rana Chatterjee, Member Secretary assisted the sub-committees. The draft report and several important issues raised during the deliberations of the meetings of the Committee, were referred to all the user State Government departments, Regional Offices of CGWB and academic institutes for their considered opinions.

The draft report and the observations received on it from various quarters were discussed at length in the meetings of the Committee before finalization of the report. The committee has also reviewed the scientific studies done in the field of ground water resources assessment in hard rock terrains and the summarized contents are annexed. The final recommendations of the committee comprise of two parts: (i) the issues/ modifications on which there was unanimity, and (ii) the issues that could not be resolved.

CHAPTER 2

REVIEW AND OBSERVATIONS OF THE COMMITTEE

2.1 REVIEW:

The Ground Water Estimation Committee 1997, shortly GEC-1997, revised the methodology GEC-1984. The important changes incorporated in the GEC-1997 are - (i) in hard rock areas the assessment is made with respect to watershed unit, (ii) the assessment is made separately for command and non-command areas, (iii) during the non-monsoon period recharge from rainfall and other sources is based on the Rainfall Infiltration Factor and other prescribed norms, (iv) the stage of development is determined considering the draft and availability for all uses instead of only irrigation, and (v) categorization of assessment unit is to be governed by long term water trends besides the stage of development.

The GEC-1997 methodology was re-looked in the light of presentations made on case studies in different types of hard rock terrain and feedback received from the State Ground Water Departments (SGDs) and Central Ground Water Board (CGWB).

2.2 OBSERVATIONS

Different aspects of the GEC-1997 were discussed at length and in all six modifications/recommendations emanated. Out of the six modifications only one namely " Categorization of Assessment Unit" could be resolved and has been duly recommended for implementation and adoption.

The remaining five modifications pertain to the accounting of the recycled ground water flow or the recharge component due to return seepage from ground water irrigation. In the GEC - 1997 the return ground water flow, termed as Rgw, has been added to the recharge from rainfall and other sources. There are serious reservations from different quarters against adding up of Rgw to the annual recharge. Because, with the increase of ground water draft and in turn the stage of development it is imperative that there will be a resultant increase in the total annual ground water recharge. On the other hand there is a school of thought in favor of retaining the Rgw, as done in the GEC-1997, for estimation of the total annual recharge to ground water. After several deliberations and discussions no consensus could be reached and the matter, hence, has been recommended for considerations by the "Standing Committee on Ground Water Resources Estimation", that is recommended to be constituted. The GEC-1997 also recommended a similar committee to pursue and take an overview of R & D activities.

Besides, it has been concern of one and all that there is a lack of adequate database to place the estimates on firm footing. In this direction detailed experimentations and studies are required to have a reliable assessment of important parameters used in the ground water resource estimation.

All the suggested modifications and aspects of the lack of data base are outlined below ;

(a) Issues recommended for implementation:

The committee has unequivocally accepted one modification related to the categorization of the assessment unit on the basis of ground water resource and trends of water level. The long term water level data should preferably be for the period of 10 years. The committee has also modified the term 'significant decline' to be of the order of 10 to 20cm per year. This modification has been recommended for implementation and adoption.

(b) Issues recommended for consideration of the "Standing Committee on Ground Water Resources Estimation":

Since no consensus has been arrived at other proposed modifications, the same are recommended for consideration of the proposed "Standing Committee on Ground Water Resources Estimation" under the GEC- 1997. These modifications and observations are related to:

1. Computation of recharge during the monsoon season in Command / Non-command areas - the issue is whether or not to exclude the recycled ground water (Rgw) term.

2. Estimation of Normal recharge during the Monsoon and Non- monsoon season: - whether or not to exclude the recycled ground water (Rgw) term as well as other issues related to normal recharge.

3. Natural loss during the Non- monsoon season: - this should be crosschecked using the equation of water level fluctuation.

4. The Stage of ground water development: - computation should be done based on the net draft instead of the gross draft.

5. It is common observation that there is a lack of database and the same should be adequately strengthened so as to arrive reliably at various parameters frequently used in ground water estimation.

2.3 CASE STUDIES IN DIFFERENT HYDROGEOLOGICAL TERRAINS

The Committee reviewed case studies on resource assessment using the GEC-1997 in different hydrogeological terrains. These were: in granitic terrain - a watershed in Karimnagar district, Andhra Pradesh, in basaltic terrain - a watershed in Latur district, Maharashtra and in limestone terrain - in few blocks in Durg and Bastar districts of Chattisgarh. The studies reflect that proper segregation of data is required on the basis of watershed and command and non-command areas. It is also observed that many parameters, like, water level fluctuations, seepage from water bodies, return flow from irrigation etc. are varying significantly from the empirical norms recommended in the GEC-1997 and these need micro-level field studies. Considering the anisotropy of the hard rock terrain, suggestions have been made to further segregate the watershed based on geomorphological and hydrogeological characteristics.

These case studies stress upon the work to be carried out to strengthen the database. A summary of these three case studies is given in Annexure III

CHAPTER 3

RECOMMENDATIONS

There are three distinct recommendations of the Committee as outlined below:

1) Issues Recommended for Implementation

The categorization of assessment unit (Block/watershed) has been rationalized and different possibilities have been considered.

2) Issues Recommended to Standing Committee

There are some issues that require revision and in-depth study for reliable estimates. It is an onerous task with differing views and has been appropriately referred to the Standing Committee to be formulated as per the outline recommended.

3) Formation of Standing Committee

To solve the outstanding issues as under recommendation (2) above and pursue R & D work, it is essential that a Standing Committee be formed with the Central Ground Water Board as nodal agency. It is reiterated that the GEC - 1997 Report, under recommendation No. 6.3.2 ( pp 78-81) emphasized to set up a similar committee.

3.1 ISSUES RECOMMENDED FOR IMPLEMENTATION

3.1.1 Categorization of Assessment Unit ;

This recommendation is to be implemented both in hard rocks and soft rocks.

(a) Long-term ground water level trend

The long term ground water level data should preferably be for the period of 10 years. The significant rate of water level decline may be taken between 10 and 20 cm per year depending upon the local hydrogeological conditions. Accordingly, in 'Detailed Guidelines for Implementing the Ground Water Estimation Methodology - 1997' page 153-154, the value of 'Z' would be read as 10 to 20 cm per year.

(b) Categorization of units

In order to remove ambiguities in the categorization by the existing methodology, the following procedure is suggested.

S.  No.	Stage of Ground Water Development %	Significant Long term Decline		Categorization
		Pre-monsoon	Post-monsoon
1	<=70%	No	No	SAFE
		Yes/No	No/Yes	To be re-assessed
		Yes	Yes	To be re-assessed
2	> 70% and <= 90%	No	No	SAFE
		Yes/No	No/Yes	SEMI- CRITICAL
		Yes	Yes	To be re-assessed
3	> 90% and <= 100%	No	No	To be re-assessed
		Yes/No	No/Yes	SEMI-CRITICAL
		Yes	Yes	CRITICAL
4	> 100%	No	No	To be Re-assessed
		Yes/No	No/Yes	OVER- EXPLOITED
		Yes	Yes	OVER- EXPLOITED

Note: 'To be re-assessed' means that data is to be checked for the purpose of categorization.2.2.6

The above modifications are to be adopted in all type of rock formations, that is, other than the hard rocks also.

3.2 ISSUES RECOMMENDED TO STANDING COMMITTEE

3.2.1 Ground Water Assessment In Non-Command Area

3.2.1.1 Computation of recharge in Monsoon Season

RG - DG -B+IS+I = S ( = h x SY x A ) (equ.2 of GEC-1997)

R- DG +Rgw-B+ IS +I = S ………….(modified)
where,
R = Recharge from rainfall and surface water sources during monsoon period
S = Ground water storage increase
RG = gross recharge due to rainfall and other sources including recycled water

RG is required to be changed to total recharge from rainfall and surface water sources only, that is excluding the recycled ground water (Rgw). Because increase in withdrawal of ground water will proportionately increase Rgw and would result in increase of the recharge.

R = S + DG (equ. 3 of GEC-1997)
(should be modified deducting the term Rgw)
R = S + DG - Rgw ……….(modified)

Rrf = R-Rgw-Rwc-Rt (eq 5 of GEC - 1997)

Rrf = R-Rwc-Rt ……….(modified)

Estimation of normal recharge during monsoon season (pp.44-45 of GEC-1997)

Criteria PD ..………(modified)
If PD is beyond the limit of 20%, the data representativeness of all the wells in the unit of assessment should be checked.

R(Normal) = Rrf (normal) + Rgw +Rwc + Rt (equ. 9 of GEC-1997)
R(Normal) = Rrf (normal) + Rwc + Rt ……….(modified)

Normal recharge should exclude the term Rgw

3.2.1.2 Computation of recharge in Non-Monsoon Season

Recharge from other sources …….…………………………(modified)

Recharge during the non-monsoon season from other sources, would include recharge from tanks (Rt), and from water conservation structures (Rwc) to be estimated from the norms given in GEC-1997. Recharge from return flow from ground water to be excluded.

Total recharge in non-monsoon season ……………….( modified)
Sum of recharge from rainfall in the non-monsoon season and recharge from other sources in the non-monsoon season excluding recharge from return flow of groundwater.

3.2.2 Ground Water Assessment In Command Area

3.2.2.1 Computation of recharge in Monsoon Season

R(normal) = Rrf (normal) + Rc + Rsw + Rt + Rgw + Rwc
(eq. 13 of GEC-1997, pp. 50)

The total recharge should be the sum of recharge from rainfall and surface water sources only, that is, recharge from ground water irrigation/ return flow from ground water (Rgw ) has to be excluded from the above. Thus,

R(normal) = Rrf (normal) + Rc + Rsw + Rt + Rwc ……( modified equation 13)

3.2.2.2 Computation of recharge in Non-Monsoon Season

Recharge from other sources ………………………………(modified)
Recharge during non-monsoon season from other sources would include canal seepage (Rc), surface water irrigation (Rsw), tanks (Rt) and water conservation structures (Rwc) are to be obtained using the norms presented in GEC-1997, and excluding recharge from return flow of groundwater (Rgw).

Total recharge in non-monsoon season ……………….(modified)
Sum of recharge from rainfall in the non-monsoon season and recharge from other sources in the non-monsoon season excluding recharge from return flow from groundwater.

Net Annual Ground Water Availability ……… (Section 5.10.1 of GEC-1997)

It is recommended that 5 to 10% of the total annual ground water recharge may be assigned to account for natural discharge in the non-monsoon season.

3.2.3 Natural Loss during the Non- monsoon season.

The figure of natural loss can also be crosschecked by using the equation of water level fluctuation for the non-monsoon period.

It is further recommended that in case the observed value of base flow in the rivers during non-monsoon season appears to vary widely from the calculated value arrived at using above mentioned norm, the Natural Loss during non-monsoon period may also be calculated as a second check using the following relationship.

Natural loss = B + Et = R - S - DG +Rgw
where,
B = Baseflow in non-monsoon season
Et = Evapotranspiration in non-monsoon season
R = Recharge from rainfall and surface water sources in non-monsoon season
S = Change in Ground water storage in non-monsoon season
DG = Gross ground water draft from all sources in non-monsoon season
Rgw = Return flow from groundwater irrigation in the non-monsoon season

3.2.4 The Stage of Ground Water Development.

The stage of development of assessment unit in the GEC-1997 is determined with respect to the existing gross draft for all uses. Since, in the proposed computation of recharge, the net draft (DG - Rgw) instead of Gross Draft (DG) has been considered, the stage of development should be done based on the net draft.

Therefore, the Stage of ground water development (%) =

Existing Net Ground Water Draft for All Uses X 100 ………(modified)
Net Annual Ground Water Availability

where, the net ground water draft is equal to the gross draft (Dg) minus the return flow from ground water( Rgw).

3.2.5 Strengthening of Database Management System

Significant hydrogeological data have been generated for the last few decades by various Central and State Govt. agencies. However, the database management system in this field has remained weak that is required to be strengthened by documentation and exchange amongst the user agencies. Data on some of the other important parameters like baseflow and evapotranspiration are quite sparse and immediate action needs to be taken to generate data on these components, in the absence of which Alternate Methodologies For Ground Water Resources Estimation cannot be tried.

a. Refinement of Norms of recharge components - There are a large number of recharge components that are estimated by adhoc norms in the GEC 1997. There is a need to utilize all available data to improve these adhoc norms and identify possible data lacunae, which must be rectified by additional studies/observations.

b. Return flow from Irrigation - A study is necessary to estimate the dominant parameters affecting the magnitude actual percentage of return flow from irrigation for different combination of these parameters.

c. Ground Water Draft - The present exercise on estimation of ground water resources based on the GEC-1997 methodology heavily depends on Ground water draft. In the absence of realistic draft data, the water balance and stage of development figure go quit disarray. Attempts should be made to have a correct number of live structures and unit draft in varying agro-climatic conditions. State govt. should issue necessary directives / pass Government Resolutions to the concerned departments for registration of ground water abstraction structures for different uses.

Further, there is an urgent necessity for focused R&D efforts on the estimation of draft. The study should aim to determine: a) the expected levels of uncertainty in draft estimates by different methods, b) the seasonal variation of draft, c) the variation of draft with respect to normal, deficit and surplus rainfall, d) the effect of long term water level trend on draft, and e) the rate of development of draft over the years in different regions.

d. Baseflow - Another important parameter intimately involved in water balance exercises is baseflow, the data on which is quite lacking. The committee recommends a policy approach to be framed at the Central and State level which would insists on providing a stream gauging station at the outlet of all watersheds in hard rock areas.

e. Spring Discharge - In high elevation aquifers, spring discharge studies have to be taken up for rainfall recharge computation.

f. Specific Yield - In hard rock terrain, the specific yield of the aquifer is highly site specific and may vary within small distance. It is therefore suggested that specific yield may be estimated for different hydro-geomorphic units.

g. Ground Water Development Worthy Areas - Assessment of ground water should be carried out only in ground water development worthy areas. There is a need to demarcate such areas.

3.3 FORMULATION OF STANDING COMMITTEE

It is recognized that refinement of the methodology of the ground water resource estimate requires extensive Research and Developmental support. It is therefore recommended that a Standing Committee be constituted. The formulation of 'Standing Committee' has been recommended by the GEC-1997 also. The Standing Committee could be named as 'R & D Advisory Committee on Ground Water Estimation'.

To reproduce recommendations of the GEC-1997, the Standing Committee would look into the following broad issues -

(A) Applicability of the recommendations suggested in Chapter 3.3 (GEC-1997) regarding computation of ground water recharge and stage of ground water development.

(B) R&D studies with reference to ground water resources estimation.

The thrust areas of the R&D activities of the Standing Committee would include -

a) Periodic revision of norms to be adopted for ground water assessment.

b) Development of state of art Data monitoring, data storage and retrieval systems, management information systems, geographic information systems and decision support system.

c) Studies on Distributed parameter modeling using finite difference, finite element and boundary integral equation methods.

d) Development of Alternative methodologies for ground water resource estimation.

e) Strengthening of infrastructure facilities with national and state level ground water organisations and upgrading the technical skill of the human resources in these organisations.

The constitution of this Committee should be as follows:

1. Chairman, CGWB Chairman
2. Member (SAM), CGWB Member
3. General Manager, NABARD, Bombay Member
4. Representatives from State Ground Water Members (2) Departments in hard rock terrains

5. Senior Scientist, CGWB Member - Secretary

The terms of reference of the Committee will be as follows:

(i). To review the scientific studies done in the field of ground water resource assessment.
(ii). To review the validity of the recommendation of GEC-1997 and, if found necessary, suggest alternate methodology for assessment of ground water resource
(iii) To firm up the recommendations of the present committee namely, "Committee for Estimation of Ground Water Resources in Hard Rock Terrain".
(iv) Any matter referred to the Committee from time to time
(v). Any other aspect relevant to the terms referred above.

For efficient working of the 'R & D Advisory Committee on Ground Water Estimation', it is also recommended that from among the members of the above committee, different working groups may be formed to assist on different aspects under the preview of the committee.