TITLE OF THE STUDY: Benefits of Tank Desiltation in Catchment and Command Area of Kolar District - An Economic Analysis
POST GRADUATE STUDENT INVOLVED:
Ms. Ramya R.D.
email: ramya_r_d@rediffmail.com
Preamble
Peninsular India has a large concentration of irrigation tanks. For centuries,
these tanks supported agricultural development in rainfed regions. These water
bodies are the common property resources owned and managed by village community.
Tanks are multifunctional, providing surface and groundwater irrigation and
serving water needs of rural households and livestock, besides silt fertilization.
Thus, irrigation tanks constructed and maintained by human efforts strengthened
agriculture in rainfed regions of south India. Of the total irrigation potential
created, tank irrigation contributed 9.4 percent while ground water irrigation
contributed to 38 percent during 1998-99.
With access to groundwater irrigation and
shift in tank management from village community to government, factors such
as siltation, unabated encroachment of tank beds for cultivation, infestation
of weeds and inadequate maintenance have been the major issues for the deterioration
of tank system.
With
severe tank siltation in recent years, there is an increasing realization for
rehabilitation of irrigation tanks. Realizing this, Government of Karnataka,
initiated the program of desiltation on pilot basis in some of the tanks in
Kolar, Bangalore and Tumkur districts in the Eastern Dry Zone.
Desiltation improves groundwater recharge
and provides silt as manure and hence be accorded top priority. Recharge of
groundwater through irrigation tank could reduce the irrigation cost by 50 percent
on per acre basis. When the irrigation cost is considered on the basis of cost
per acre-inch of groundwater, the advantage realized by farmers due to the impact
of irrigation tank are by way of savings in cost per acre-inch of water used.
These advantages are measured in terms of net returns per acre-inch of water
(Rs.1866 as against Rs. 1577).
Due to the effect of tank desiltation, the
number of functional wells and average age of wells in desilted tank village
are higher than in non-desilted tank village. Hence the well failure problem
can be controlled by groundwater recharge from desiltation program and also
the yield of wells in desilted tank village was greater than in non-desitled
tank village.
Objectives of the study
- Estimation of economic benefits of tank rehabilitation in command and catchment
areas.
- To estimate the benefits due to conjunctive use of tank and groundwater.
- Estimation of financial feasibility of investment in tank rehabilitation.
Major Findings of the study
- Under farmers not applying silt (FNAS) group, ragi occupies major area (32
percent) as it is a staple food followed by tomato (26 percent) and potato
(25 percent) as they are better suited to agroclimatic conditions. The common
crops grown by both FAS and FNAS were ragi, tomato, and potato. Maximum silt
of ten tractor loads per acre (13 percent) was applied to groundwater irrigated
crops like cauliflower, beans and sugar cane. Minimum silt of two tractor
loads was applied to ragi.
- Dependency on tank by farmers in the study villages (Chatrakodihalli, Gopasandra
and Ammernahalli) was considered under two situations of 'before' and 'after'
desiltation. Before desiltation, 2.5 per cent of farmers in Chatrakodihalli,
applied silt and after desiltation 37 percent of farmers applied silt in the
tank command in the year of silt removal.
- In the tank command, there were 79 irrigation wells of which 78 percent
were deep bore wells. Hence, farmers did not use the tank water for surface
irrigation but for domestic use. The dependency of sample farmers on irrigation
tank for different purposes like silt, irrigation, domestic use, bathing and
brick and tile making has been modest and remained unchanged before and after
desiltation. However, the dependency of livestock on tank water has increased.
- In Chathrakodihalli (desilted tank village) farmers mentioned that (i) availability
of other types of manure (24 percent), (ii) income constraint, (ii) distant
location of fields, (iv) non-availability of labour, and (v) poor quality
of silt as factors responsible for farmers not applying silt. However, in
Ammeranahalli, main reason stated for not applying silt was the poor quality
of silt from the tank.
- In desilted tank (non-desilted tank) village 80 (62) percent of dug wells
were functional and 20 (38) percent were non functional. Here the problem
of well failure was controlled to some extent by the groundwater recharge
due to desiltation program.
- The yield of bore wells and dug wells (during kharif and summer) was higher
in desilted tank village than in non-desilted tank village. During kharif,
yield of dug well increased by 46.3 percent (434 GPH). During summer, an increase
of 35.5 percent was observed in the yield of wells (214 GPH) after desiltation
due to groundwater recharge effect. In the case of bore wells, there was an
increase of 24.8 percent (376 GPH) during kharif and 22.6 percent increase
during summer after desiltation.
- When the impact of tank silt on productivity and net returns for different
crops was considered, the increase in net returns per acre ranged between
two percent and ten percent. The net returns per acre for major crops like
Tomato. Potato, ragi and Cauliflower were higher for farmers who applied silt
compared to farmers who did not apply silt. This has been the result even
after a span of eight years after silt application. This demonstrates the
positive but modest impact of silt application on net returns. This also supports
the sustainability hypothesis that the benefits of desiltation will last longer
even though the practice of regular silt application is affected. The net
returns per acre-inch of water used were higher (Rs.1720) for FAS than FNAS
(Rs.1671) by three percent. Net returns per farm were Rs.10, 166(Rs.10, 088)
for FAS (FNAS) group.
- Irrigation tanks considered in this study were desilted during 1993-94.
At the time of field survey, farmers expressed that the benefits of desiltation
like the recharge of groundwater would accrue after a period of one year.
In desilted tank village, the amortized cost per acre-inch of water was Rs.109,
which is lower by 22 percent when compared with amortized cost per acre-inch
of water used in non-desilted tank village (Rs. 134). In non-desilted tank
village farmers are extracting less water for every rupee invested on irrigation.
Ground water irrigation cost per acre was Rs. 938 in non-desilted tank village
while it was Rs. 872 in desilted tank village lower by seven percent. Correspondingly
an increase in net returns per acre was 12 percent.
- The partial budgeting analysis demonstrated that even though benefits from
silt application is modest, they are sustainable. The application of good
quality silt to the soil enhanced its fertility. There was cost reduction
due to silt application as it substitutes for manures and fertilizer. In the
case of potato crop there was an increase in net return by Rs.180 per acre.
There was decrease in cost of inputs due to silt application by (Rs. 236 per
acre). Therefore, the net gain from silt application was Rs.320 per acre.
In tomato (potato), the additional net returns of Rs.251 (Rs.320) per acre
were due to silt application Here, there was decrease in cost of inputs due
to silt application by (Rs.73 per acre). The net gain from silt application
was Rs.252 per acre.
Feasibility of tank rehabilitation
- Considering that the benefits from desiltation accrue for 20 years, the
IRR in Chathrakodihalli tank was 13.07 per cent and NPV was Rs.1, 062 per
acre. Discounted cash flow measures indicate that the desiltation is an economically
worthwhile proposition.
B. RESEARCH CONDUCTED IN NORTHERN DRY AGROCLIMATIC ZONE
TITLE OF THE STUDY: Optimal Extraction
of Groundwater Resource in Canal, Tank and Well Irrigation Commands in Karnataka-
Application of Control Theory
POST GRADUATE STUDENT INVOLVED:
Sri. Rajendra. A.
email: rajvagta@rediffmail.com / rajvagta@yahoo.co.in
Preamble
Property
rights to groundwater are obscure. However, as groundwater is indispensable
for irrigation, in the absence of alternative sources of irrigation, farmers
are desperate in searching alternative sources of groundwater. In the process,
farmers in all likelihood cause cumulative interference by drilling additional
well(s) and/or deepening existing well(s). In this study, the pattern of extraction
of groundwater is being studied under three situations where (i) irrigation
wells are located uninfluenced by recharge from any surface water body (GWSI),
(ii) irrigation wells are located under the command of tank irrigation (GWTI)
and (iii) irrigation wells are located under the command of canal irrigation
(GWCI). It has been found that farmers in GWSI have relatively low relative
sustainability index since, they compare their economic performance with farmers
who have reaped the highest net return per rupee of water.
It
has also been found that GWCI farmers with access to larger volume of groundwater,
realized higher net return per rupee of groundwater of Rs. 5.30 (Even though
high groundwater users of GWTI realized a net return of Rs.5.8 per rupee of
groundwater, the net return of Rs. 5.30 per rupee of groundwater realized by
GWCI farmers is taken as RSI base, since the recharge potential of GWCI is larger
than GWTI and hence the net return of Rs. 5.30 per rupee of groundwater under
GWCI is more sustainable than the net return of Rs. 5.80 under GWTI ) and thus
have relatively larger relative sustainability index (RSI) (of 1.00). There
are no compelling reasons to disbelieve that GWSI farmers with low RSI will
not strive towards the performance of farmers in GWCI and in the process contribute
to cumulative well interference externality. This study provides an optimal
path of groundwater extraction considering the cost of extraction as well as
the externality cost.
Objectives of the study
- To document the pattern of groundwater extraction and cropping pattern.
- To document the pattern of investment in irrigation wells.
- Examine the resilience and strategies of farmers in response to economic
scarcity of water in the framework of optimal control theory in exclusive
commands of canal, tank, and well irrigation.
- Valuation of synergistic role of canals and tanks in groundwater recharge
and associated equity implications.
Major Findings of the study
- In the study area there is a high degree of similarity between the cropping
pattern for the period 1990-91 to 1999-2000.Thus the overall distribution
of acreage under the different crops remained uniform over the last decade.
- In Bailhongala, Saundatti and Ramdurga taluks importance was given to pulses,
oilseeds and cotton with respect to crop land allocation, while in Khanapur
paddy and sugarcane were the preferred crops.
- In Bailhongala taluk, bore well served as major source of groundwater, while
in Khanapur, Saundatti and Ramdurga both bore well and open wells were in
use for irrigation.
- Saundatti taluk being closer to head reach of Malaprabha dam, the area irrigated
by surface water should have been higher than groundwater. However it was
found that the area irrigated by groundwater was higher when compared with
area under surface water. While in Ramdurga which is in mid reach Malaprabha
dam, the area irrigated under surface water was higher than the area under
groundwater.
- In GWSI 84 percent of wells were bore wells of which 70 percent were functioning
and in GWTI and GWCI, 75 percent of well were bore wells and 90 percent were
functioning.
- The over all failure rate of irrigation well in the study area was 18 percent
of which 70 percent of wells were in GWSI.
- In GWSI for every failed well there was three functioning wells, while in
tank and canal command for every failed well there were seven and 18 functioning
wells respectively.
- In GWCI the area irrigated per well is 52 percent higher compared to GWSI
and is 37 percent higher for GWTI farmers when compared to GWSI farmers.
- In GWSI Low water user (LWU) formed 53 percent and devoted 50 percent of
Gross irrigated area (GIA) for low water intensive crops such as jowar, groundnut,
sunflower. In GWTI medium water user (MWU) formed 43 percent and devoted 65
percent of GIA for water intensive crops like vegetables, maize, sugarcane
and cotton and in GWCI 73 percent of sample size were high water users (HWU)
and have devoted 80 percent of GIA under water intensive crops.
- There was inequality in access to water and in area irrigated, as GWTI and
GWCI farmers had access to surface water in addition to groundwater from wells.
Thus, devoted more than 60 percent of GIA for water intensive crops. GWSI
farmers were had greater crop diversity compared with GWTI and GWCI farmers.
- There was equality in distribution of functioning wells across groundwater
situation. In GWSI, Lower water users had 55 percent of gross groundwater
irrigated area (GGWIA) and 56 percent of functioning wells. In GWTI, Medium
Water Users had 48 percent of GGWIA and 43 percent of functioning wells and
in GWCI, High Water Users had 75 percent of GGWIA and 74 percent of functioning
wells.
- In GWTI and GWCI, 75 percent and 80 percent of GIA is irrigated by groundwater
respectively. Thus the role of groundwater in receding even under surface
irrigation pointing to the vagaries of rainfall.
- Even though the number of functioning wells per farm was almost same across
GWSI, GWTI and GWCI, there was inequity with respect to total water use. The
additional area brought under irrigation was 1.5 and 3.5 acres per well in
case of GWTI and GWCI respectively. Thus, there was higher GIA with GWCI farmers.
- MWU and HWU had higher access to water to the extent of 18.5 percent and
52.5 percent per acre when compared with LWU respectively.
- The amortized cost per well was lower by 25 percent and 30 percent for tank
and canal command farmers compared to sole well regime farmers.
- With the failure rate of irrigation well being modest (5%) in GWCI, the
externality cost per well is Rs 235, while for GWSI it was Rs 2,598 and for
GWTI Rs 655.
- The synergistic effect of surface water recharge from tank and canal has
reduced the investment per functioning well to the extent of 32 percent and
29 percent in GWCI and GWTI respectively compared to GWSI farmers.
- GWSI farmers had access to 26 percent of Groundwater and 47 percent of amortized
cost. GWTI farmers had access to 34 percent of groundwater and shared 28 percent
of amortized cost and GWCI farmers had access to 40 percent of groundwater
and shared 24 percent of amortized cost.
- The amortized cost per acre of Gross Groundwater Irrigated Area (GGWIA)
was lower to the extent of 49 percent and 39 percent for GWCI and GWCI farmers
compared to GWSI farmers. Thus to get one acre inch of water GWCI farmers
incurred 54 percent lower cost when compared with GWSI farmers.
- Amortized cost per functioning well was Rs 8,558 in GWSI, while in GWTI
and GWCI it was lower by Rs 3,059 and Rs 3,858 respectively.
- In GWSI, LWU and MWU are relatively efficient as they realized higher net
returns of Rs 200 per acre -inch of water.
- In GWTI, HWU were enjoying the benefit of low cost per acre of water as
it was relatively lower (Rs 40) than MWU and LWU. HWU are efficient as they
realized higher net return per acre-inch of water compared to LWU.
- MWU group of GWCI were the most efficient users of water as they realized
highest net returns per acre-inch of Rs 255 water among all the 9 groups.
- The cost incurred for every acre inch of water of water was the least in
GWCI of Rs 43, while in GWSI it is 3 times that of GWCI farmers (Rs 122) and
from every one rupee of investment GWSI farmers extracted 0.008 acre inch
of water, and tank command farmers extracted 0.017 acre inch and GWCI farmers
extracted 0.023 acre inch of water. Thus GWCI farmers accessed 3 times more
than sole well regime for every one rupee of investment. However the net returns
per rupee of groundwater was highest for GWCI followed by GWTI and GWSI.
- In GWCI the amortized cost per acre-inch of water was lower by 65 percent
and for GWTI farmers it was lower by 53 percent compared with GWSI. But GWCI
farmers could realize only 15 percent additional net return per acre-inch
of water compared with GWSI.
- Farmers in GWCI and GWTI have 183 percent and 110 percent higher access
to water for every rupee of investment than GWSI, as synergistic effect of
surface water has contributed for higher access at lower cost.
- In GWSI optimal extraction extends the well life by another 12 years and
the net additional benefit over the myopic extraction is Rs 5,175.
- In GWTI optimal extraction extend the well life by about 24 years and additional
Present value net benefit (PVNB) is Rs 36,573
- In canal regime optimal extraction extends the well life by about 42 years
and additional PVNB of Rs 77,020.
Implications
- The projected net return under optimal rule exhibits gradual decrease of
net return over the life horizon of irrigation well. Thus, benefit of maximum
principle from control theory is in terms of realization sustainable extraction
of groundwater. Obviously this calls for coping mechanisms inter alia reduction
in gross irrigated area with existing cropping pattern or installation of
water saving devices and water use efficient technologies.
- The cost per acre- inch of groundwater is lower in canal regime due to synergistic
effect of surface water. It is imperative that the optimal extraction will
not only promote sustainability of groundwater extraction, and dampens the
groundwater cost.
- In canal regime 75 percent of Gross irrigated area is irrigated by groundwater
due scarcity of canal water. Thus farmers need to be motivated to invest on
backstop technologies rather than investment on new wells, which are increasingly
becoming challenging venture due to cumulative well inference.
C. RESEARCH CONDUCTED IN CENTRAL DRY AGROCLIMATIC ZONE
TITLE OF THE STUDY: Valuation of Synergistic
Role of Canals and Tanks in Groundwater Recharge in the Framework of Optimal
Control Theory
POST GRADUATE STUDENT INVOLVED:
Ms.Chaitra B.S.
email: chaitra_ballal@rediffamail.com
Preamble
The groundwater extraction in pockets of Central Dry Zone dominated by coconut
crop, does not seem to be exploitative in nature. This is reflected by the modest
amortized cost of groundwater irrigation ranging from Rs. 156 per acre-inch
in GWSI (sole wells), Rs. 104 per acre-inch in GWTI (groundwater extraction
under tank command) and Rs. 73 per acre-inch in GWCI (groundwater extraction
under canal command). The net return per rupee of groundwater is the highest
in GWCI (Rs. 4.7), followed by GWTI (Rs. 3.22) and GWSI (Rs. 1.83).
The
economic access of GWCI farmers was higher by 118 percent over GWSI, and that
of GWTI was higher by 50 percent over GWSI. The net returns per acre-inch of
groundwater is Rs.337 in GWCI followed by Rs.332 in GWTI and Rs.286 in GWSI.
It was found that GWSI had greater diversification of crops compared with GWTI
and GWCI. Area under groundwater irrigation formed 85 percent of gross irrigated
area in GWTI and 65 percent in GWCI. The focus of the study is to analyse the
synergistic effects of canals and tanks in groundwater recharge and to estimate
the optimal path of groundwater extraction in Tiptur and Turuvekere Taluks of
Tumkur district.
Objectives of the study
- Estimation of optimal path of groundwater extraction under exclusive canal,
tank and well irrigation commands.
- Valuation of synergistic role of canals and tanks in groundwater recharge
and associated equity implications.
- Examination of emerging economic opportunities for farmwomen in groundwater
irrigation.
Major Findings of the study
- In GWSI optimal extraction extends well life by seven years and net additional
benefits over myopic extraction was Rs.36998, while in GWTI (GWCI) optimal
extraction enhances the well life by 17 (24) years and present value of net
additional benefits were Rs. 85840 (Rs.163653).
- In GWTI optimal extraction enhances the well life by 17 years and present
value of net additional benefits were Rs. 85840.
- In GWCI optimal extraction enhances the well life by 24 years and present
value of net additional benefits were Rs. 163653.
- The cropping pattern was mainly dominated by commercial perennial coconut
plantations in GWSI (88 percent) compared to GWTI (55 percent) and GWCI (61
percent). The paddy crop was prominent in both GWTI (14 percent) and GWCI
(20 percent).
- In the study area, 80 percent of irrigation wells were borewells. Dug wells
and Dug- cum- bore wells in GWSI are completely Un-fructuous. On the contrary,
all the dug-cum-borewells, 60 percent of dug wells were productive in GWTI,
while in GWCI all the dug wells and 66 percent of dug -cum-bore wells were
functional. In the case of borewells, rate of failure was higher in GWSI (35
percent) compared with GWTI (12 percent) and GWCI (10 percent).
- Depth of the bore wells was the highest in GWSI (300 feet) followed by GWTI
(200 feet) and GWCI (180 feet). Which reflects relatively higher water table
in canal and tank command due synergistic effect of groundwater recharge from
surface water bodies.
- Average yield of wells were comparatively higher in GWCI (2794 GPH) and
GWTI (2360 GPH) than GWSI (1692 GPH) due to recharge from surface water bodies.
- Proportion of area under groundwater irrigation to gross irrigated area
was 85 percent and 65 percent in tank command (GWTI) and canal command (GWCI)
respectively, thus emphasizing how vital groundwater irrigation is even in
command areas of tanks and canals.
- Net returns from groundwater irrigated area were accounted for 88 percent
(67 percent) of total net returns in GWTI (GWCI) and the rest were from surface
water irrigated area.
- Net returns obtained per acre of gross irrigated area was found to be highest
in the case of GWCI (Rs.4582), followed by GWTI (Rs.4096) and GWSI (Rs.2915).The
net income received per acre inch of water in GWCI (Rs.337) was the highest
followed by GWTI (Rs.332) and GWSI( Rs.286).Thus, synergistic effect of surface
water bodies facilitated realization of higher incomes over GWSI due to recharge
of wells, which dampen the failure of wells.
- Cropping intensity and irrigation intensity was found to be increasing from
GWSI to GWTI to GWCI.
- The amortized cost per well was higher by 25 percent and 35 percent for
GWSI farmers compared with GWTI and GWCI farmers. While, amortized cost per
functioning well in GWSI was nearly twice (Rs.8067) than that of GWCI (Rs.4850).
- In GWTI (GWCI) amortized cost per acre-inch of groundwater was lower by
34percent (54 percent) compared with GWSI which reflects positive externality
due to synergistic role of canals and tanks in groundwater recharge.
- The failure rate of irrigation wells being modest in GWTI (12 percent) and
GWCI (10 percent), the externality cost per well is Rs.387 and Rs.422 respectively,
while in GWSI it is Rs.2051.
- The synergistic effect of surface water bodies has reduced the investment
per functioning well to the extent of 27 percent and 28 percent for GWTI and
GWCI farmers respectively compared with GWSI farmers.
- Economic access in terms of groundwater used per rupee of amortized cost
was relatively higher for GWCI farmers (0.0137 acre-inches) than GWTI (0.0096
acre- inches) and GWSI (0.0064 acre -inches) farmers.
- In sole well regime (GWSI). HWU incurred relatively lower (Rs.132) amortized
cost per acre- inch of water than MWU (Rs.167) and LWU (Rs.156). Thus, HWU
had greater economic access (0.00759 acre- inches) compared with LWU (0.00641
acre- inches) and MWU (0.00591 acre - inches).
- In GWSI, HWU realized higher net returns (Rs.309) per acre- inch of water
compared with MWU (Rs.274) and LWU (Rs.288).
- In GWTI, LWU realized highest net returns (Rs.346) per acre-inch of water
followed by MWU (Rs.287) and HWU (Rs.241).
- In GWTI, MWU had greater economic access to groundwater (0.0102 acre inches)
than HWU (0.0098) and LWU (0.0089 acre inches) as cost incurred per acre-
inch of groundwater was lowest for MWU (rs.98) followed by HWU (Rs.102) and
LWU (Rs.113).
- In GWCI, eventhough HWU had greater economic access to groundwater ,net
returns per acre inch of water was higher for LWU to the extent of 7 percent
(45 percent) compared with MWU(HWU).
- Increased well life, negligible well failure and increase in the water yield
of the wells are some of the main physical impacts of the synergistic effect
of surface water bodies in groundwater recharge. The economical impacts are
in terms of lower irrigation cost and higher income from their irrigated lands.
- Percentage of woman labour employed was higher (34 percent) in GWSI compared
with GWTI (31 percent) and GWCI (25 percent) as crop diversity was better
in GWSI. While percent female labour employed in surface water irrigated farms
was higher because, large portion of cropped area was under paddy crop where
as in groundwater irrigated area, cropping pattern was dominated by coconut
gardens.
Implications
- As discounted net returns and well life are improving in the optimal extraction
compared with myopic extraction, withdrawal of groundwater based on optimal
control results in sustainable extraction.
- Rainwater harvesting for recharging groundwater in non-tank or canal command
reduces the groundwater extraction cost. Hence efforts be made in this direction.
- Farmers need to be motivated to invest on backstop technologies like drip
irrigation rather than investing on new wells which is increasingly becoming
a risky venture.
- Since installation of electrical meter on IP sets is inviting resistance
from farmers, water meter can be fixed initially to educate farmer regarding
the volume of extraction of groundwater on their farm. This helps in budgeting
groundwater for different crops. Later, farmer can be convinced to defray
electrical charges.
This research paper is published in Water Policy Journal, IWA Publishing, 2005.
Click here
to Download this paper: Chaitra, B.S. and Chandrakanth, M.G. (2005),
Optimal extraction of groundwater for irrigation: synergies from surface water
bodies in tropical India.Water Policy Journal, IWA Publishing, 7: 597-611.
.