Large scale exploitation of groundwater resources particularly after 1970 has enabled us to meet the requirement of water for different purposes like irrigation, industrial and domestic needs. But due to lack of proper management and monitoring of groundwater resources, following undesired effects have crept in.
In the hard rock terrain of Andhra Pradesh, Karnataka, Tamil Nadu, Maharashtra and parts of Madhya Pradesh and Gujarat States, steep decline of water levels forced the farmers to go for deep bore wells upto the depth of 500 meters. The successful wells which were constructed within the weathered rock and upper portions of jointed hard rock during 1970’ and 1980’became defunct. After 1980’s the bore wells are being located in deep Fractured zones. But the success rate of such bore wells is very low and even in the case of successful bore wells, they became dry after 2-3 years of operation. All these things led the farmers to undergo a lot of hardships. In addition, there is burden on power sector due to transformation of shallow wells to deep wells, in as much as the consumption of power has been increased considerably. The state wise and district wise areas affected by over exploitation of groundwater are given below:
1. Andhra Pradesh— Karimnagar, Warangal, Nalgonda, Mahaboobnagar, Nizamabad, Chittoor, Anantpur and parts of Kurnool and Kadapa districts.
2. Tamil Nadu-- Coimbatore,Salem,Dindigal,Erode districts.
3. Maharashtra—Ahemadabad,Solapur,Osmanabad,Pune,parts of Sathara and Sangli districts.
4. Karnataka--- The area covered by Precambrian hard rocks.
5. Madhya Pradesh- Malwa plateau comprising of Indore, Rathlam, Ujjain, Jabua, Nimach districts and parts of eastern M.P covered by Precambrian hard rocks.
In the above districts, however, the areas coming under canal command, valley fill areas, tanks and Lake command areas, buried river channels , along stream courses are not affected by over draft conditions.
Under the above circumstances, the artificial groundwater recharge assumes significance as an effective tool for mitigating water scarcity in the over exploited areas. In this context, Rural Development Ministry attaching due priority has allocated considerable amount for this purpose. One of the main beneficiaries of the artificial recharge of groundwater is the power sector. Once the water levels improve, the power consumption of irrigation wells will be reduced appreciably.
Following is an attempt to work out the benefits on the power front due to artificial recharge
of groundwater schemes watershed wise.
To calculate the effects of Watershed Development through artificial recharge of groundwater, a watershed is assumed to be comprising of 25 villages with 120 number of irrigation wells per village.
Parameters assumed:
1. Watershed ---- 1
2. No. of villages ----- 25
3. No of existing irrigation wells -- 120
4. No of working hours of each
irrigation well annually -- 1000
Discharge of well -- 5 lps
Cost of energy -- Rs.1.79 per unit
With the above parameters the input power required for the pumpset in KW has been
calculated using the following formula.
Q X H X 0.746
KW = -------------------------------------------
76 X Pumpset effi X motor effi
Where Q is discharge of irrigation well in LPS
H is total head in meters
Pump efficiency has been taken as 70%
Motor efficiency has been taken as 80%
As an example, average hydrogeological conditions of Mahabubnagar district have
been taken. The average discharge of irrigation well has taken as 5 lps, total head
of 17 meters. The values substituted in the formula:
5 x 17 x 0.746
KW = ------------------ = 1.51 KW
0.7 x 0.8 x 75
It is assumed at this stage, artificial recharge (water harvesting) of groundwater project has taken up and after few days there is improvement in water levels of irrigation wells located In the watershed. Along with water level improvement, the discharge of wells also increases. For 1M improvement the discharge increase has taken as 5%, for 2M,8%,for 4M,20% and for 8M,50% increase in yield of well has taken. The input of power in KW is calculated for 1m, 2m, 4m and 8m as given below:
5.25 x 16 x 0.746
1M = ---------------------- = 1.492 KW
0.7 x 0.8 x 75
Similarly, KW values calculated for 2M,4M and 8M.
The number of units (Kwh) saved for 1M, 2M, 4M and 8M calculated using the following formula.
E = P x N x W
E is energy in lakh units (L.U) saved
P is the difference of connected load in base level and at 1M
N is average working hours per well annually
W is No of wells in watershed.
The above procedure adopted for 2M, 4M and 8M.It is observed that with 1M water level improvement, 0.60 L.U, for 2M improvement 2.10 L.U, for 4M improvement 3.90
L.U and for 8M 9.30 L.U are saved.
Sl.No | Improvement in water level (M) | No.of units(Kwh)saved in L.U | Cost of energy per unit in Rs. | Cost of energy saved in Rs.Lakhs |
1 | 1 | 0.60 | 1.79 | 1.07 |
2 | 2 | 2.10 | 1.79 | 3.76 |
3 | 4 | 3.90 | 1.79 | 6.98 |
4 | 8 | 9.30 | 1.79 | 16.65 |
Taking the saving of connected load in KW for 1M, 2M, 4M and 8M, total connected load for 3000 wells is calculated. From these values additional number of wells feasible in watershed are shown in the following table:
Sl.No | Water level improvement in (M) | Saving In KW | No of wells in wateshed | Total KW for 3000 wells | Addl no of wells feasible taking 3.73Kw per well |
1 | 1 | 0.02 | 3000 | 60 | 16 |
2 | 2 | 0.07 | 3000 | 210 | 56 |
3 | 4 | 0.13 | 3000 | 390 | 104 |
4 | 8 | 0.31 | 3000 | 930 | 249 |
The above values may differ with the actual field conditions, like actual discharge, static water level, improvement in water level, number of pumpsets, working hours etc. The amount spent on artificial recharge of groundwater project can be realized to some extent due to savings in power consumption.
If three watersheds of same size as above are developed through artificial recharge of groundwater, about 30 lakh units can be saved which is equivalent to one MW of installed capacity. It is worthwhile to mention here that for 1MW installed capacity, 5 crores investment is required not to speak of the gestation period of 3-4 years.
ARTIFICIAL RECHARGE PROJECTS IN WATERSHED vis-à-vis INVESTMENT SAVED IN POWER SECTOR.
As per the data published in the paper “Central Sector Scheme-Artificial Recharge to Groundwater” published in the workshop on Rainwater-Harvesting conducted during 15th to 16th December 2001 in IIT Chennai, the cost of Rainwater Harvesting Structure ranges from 4.0 to 13.50 lakhs giving an average of Rs 8 to 9 Lakhs per village. For a watershed of 25 villages, the cost will be about 200 lakhs and for 3 watersheds it is about 6 crores.
Though the above investment appears to be same as that required for additional generation, investment in Artificial Recharge of Groundwater is preferable for the following reasons.
Gestation period is small, compared to the setting up of unit for additional generation of power.
The associated problems of fuel products, higher degree of maintenance and administrative problems are avoided in the case of artificial recharge of groundwater schemes.
Though the additional generation of power will enable energisation of additional agricultural pumpsets, the depletion of water levels in the existing wells leads to drying of wells. Artificial recharge of groundwater schemes not only help adding more no of feasible wells due to saving of power, it can also sustain the satisfactory working of existing wells due to improvement in water level and yield of wells.
The Artificial Recharge of Groundwater methods can save the power and thereby help the power utilities to improve financially. In view of this, the financial institutions which are financing power utilities for various categories of schemes can also extend the finances to Artificial Recharge of Groundwater Schemes.
Finally, to quantify the actual benefits derived from Artificial Recharge of Groundwater Schemes, the following data is to be collected before and after implementation of schemes.
Measurement of water levels and Discharge of Irrigation wells in watershed before and after implementation of artificial recharge schemes.
All the irrigation wells in the watershed should have meters to monitor the power consumption before and after completion of projects.
The net and gross irrigated area per irrigation well before and after construction of artificial recharge schemes to be recorded.
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Sri Satyanarayana garu,
ReplyDeleteThis is one of the best and most informative blogs I ever read since the blog revolution started.
When I read your blog I started to feel how much can be done to improve our lives in India. Thanks to Sita Prasoona (your niece and my very good friend) through whom I came to know about your blog and I am very much impressed with its content. I will do my bit of social networking for your blog and help people get enlightened with facts and figures.
Thanks once again,
Warm Regards,
Prashanth Rayaprolu
Dear Satyanarayana garu,
ReplyDeleteSubject covered in the topic is very interesting and useful for experts as well as general public. I personally wonder, how the public or government agencies are allowing burying ponds and lakes in cities. If they cannot create new ponds, at least they should not allow burying of lakes (Government agencies should permit building of houses on ponds like boat houses, instead of burying lakes and constructing houses). Also I could not understand, whether a lake simply as it is can be useful for water re harvesting without any maintenance as I observe that a pit dig for 2 or 3 meters depth will become as a storage tank without any percolation/ sinking of water within one year. I hope government agencies will undertake some better methods to ensure percolation of water in lakes and especially at flood inundating areas on city roads. Digging deep open wells in 200 yards space nearby flood prone city junctions and diverting water from such flooding junctions shall save lot of water from flowing away through Moosi river as well as saving public from hardships of traffic jams. I am not aware of Air compressor pumps. I hope, you cover some details on different types of pump sets availability and guide lines for capacity selection. Here, I would like to mention that control panels available for single phase prevention, dry run prevention and automatic switching on and off of pump sets in domestic as well as agricultural pump sets shall be much useful to avoid burning of pump sets as well as avoiding farmers to stay in fields during day and nights to switch on pumps during frequent power cuts.
@Srinivas :Thanks for going through the article on Artificial recharge of groundwater a tool for saving power.If you
ReplyDeleteFind the area under irrigation in Andhra Pradesh in last 50 years, you will find area under Groundwater,Canals and other sources increases but area under Lakes and Ponds decreased drastically The main reason are, lack of maintenance and encroachments.The bottom o f lakes are heavily silted and prevents recharge to groundwater.Few years back Govt started programme of removing the clay from the bottom of Lakes and Ponds during summer season and the same will be taken by Farmers to utilize the clay in their fields. If it continues every year, it is beneficial to both Farmers and to groundwater recharge.
Regarding your suggestion of construction of deep dugwells near the junctions of flooded areas,already in some cities, flood drains are constructed to allow the flood water to flow to Streams or Rivers.But it is still useful to construct some deep pits in the flood drains itself in selected locations so that part of flood water goes to groundwater.During rainy season it will take more than one month for rainwater to infiltrate to groundwater basin. Hence during heavy rains atleast in the first one month of rainy season groundwater basin can accept flood water percolation.It is still a better option to construct Storage tanks in the upper catchment areas and divert the flood water (even against gravity) which will Recharge the groundwater basin throughout year.
The Air compressor pumps are used in deep bore wells (more than 1000feet)instead of Submersible pumpsets when the discharge and recouperation of wells are very poor.However the efficiency of pumpsets is very low. In western portion of Tamil Nadu these pumpsets are common.Even In Hyderabad city also in few localities these Air Compressor pumpsets are being used.
Regarding your suggestion of control panels for single phase prevention,dry run prevention and automatic switch on and off of pumpsets-if they are available,farmers opt for them It is very useful both for farmers and power utilities.