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Water balance study and
conjunctive water use
planning in an irrigation canal
command area: A remote
sensing perspective
V. V. Rao a & A. K. Chakraborti a
a Water Resources Group, National Remote
Sensing Agency, Balanagar, Hyderabad, 37, India
Published online: 25 Nov 2010.
To cite this article: V. V. Rao & A. K. Chakraborti (2000) Water balance study and
conjunctive water use planning in an irrigation canal command area: A remote
sensing perspective, International Journal of Remote Sensing, 21:17, 3227-3238,
DOI: 10.1080/014311600750019859
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int. j. remote sensing, 2000, vol. 21, no. 17, 3227–3238
Water balance study and conjunctive water use planning in an
irrigation canal command area: a remote sensing perspective
V. V. RAO and A. K. CHAKRABORTI
Water Resources Group, National Remote Sensing Agency, Balanagar,
Hyderabad-37, India; e-mail: valav@hotmail.com
Abstract. Water budgeting of the D-36 and D-36 A distributaries conŽ ned
between Pedda Vagu, Korutla Vagu and Kakatiya main canal of the Sri RamSagar
Project (SRSP) Command area was conducted using remote sensing derived crop
areas, land cover information, irrigation tank inventory and source-wise distribu-
tion of irrigated areas, together with conventional meteorological, canal  ows
and well inventory data. A semi-empirical water balance model was developed
and validated using remote sensing derived objective information of the command
area and the validated model used for predicting the groundwater table under
normal rainfall conditions. Recharge and water balance in the study area indicated
3
that the net recharge to the aquifer is negative to the tune of 2.54Mm resulting
in a fall of the groundwater table by 0.79m during 1992–93. However, normalized
groundwater recharge and water balance estimates indicate an impending
waterlogging problem with an annual groundwater table rise of 0.35m. In view
of existing water management practices, a conjunctive water use plan of rotational
operation of aquifers and canals is suggested.
1. Introduction
Judicious management of the water resources of a groundwater basin needs a
comprehensive understanding of the total system and its response to recharge. An
adequate estimate of the availability of groundwater storage in a basin requires
water budgeting. Water budgeting helps to evaluate the net available water resources,
both surface and subsurface, and to assess the impact of existing water utilization
pattern and practices. The need for accurate and reliable information on crop
inventory, land cover, soils, source-wise distribution of irrigated areas and irrigation
tank inventory, has often precluded quantitative description and analysis of various
processes that describe the water resources regime in any irrigation command. The
emergence of remote sensing as a tool for providing the above-mentioned base-line
information not only in a spatial dimension but also to monitor them through time,
is cost and time eŒective. This information, together with the conventional meteorolo-
gical, canal  ows and well inventory data can be used as inputs to the various
existing empirical, semi-empirical and conceptual models to understand the various
components of water budgeting. This constitutes the scientiŽ c basis for development
of guidelines for planning sustainable use of groundwater resources in conjunction
with surface water resources in the irrigation command area. In recent years there
Paper presented at ICORG ’97 International Conference on Remote Sensing and
/
GIS GPS, Hyderabad, India, 18–21 June 1997.
International Journal of Remote Sensing
ISSN 0143-1161 print/ISSN 1366-5901 online © 2000 Taylor & Francis Ltd
http://www.tandf.co.uk/journals

3228
V. V. Rao and A. K. Chakraborti
has been more emphasis on groundwater development in irrigation projects and on
the planned conjunctive use of canal water and groundwater to augment canal
supplies and control waterlogging and salinity, thereby increasing the reliability of
irrigation system operation. This fact is duly recognized in India and constitutes one
of the strategies for sustainable development of irrigated agriculture (Ministry of
Irrigation 1984, Government of India 1985).
The groundwater estimation committee (Ministry of Irrigation 1984) recognized
the availability of groundwater potential in major irrigation projects and recom-
mended speciŽ c empirical constants to estimate the recharge from the conveyance
and distribution system of these projects. These constants are now routinely applied
by the various government agencies to estimate the groundwater potential of a
region. The methodology is based on such speciŽ c empirical constants, which are
modiŽ ed based on objective information derived from satellite remote sensing data
and Ž eld data, for estimating the groundwater recharge and annual water balance
of the study area.
2. Study area
The study area for this paper lies between 78ß 41 to 78ß 48 E longitude and
¾
¾
18ß 44 to 18ß 53 N latitude and is conŽ ned by two tributaries: Pedda Vagu and
¾
¾
Korutla Vagu of the river Godavari and the Kakatiya main canal of the SriRamSagar
project (SRSP), with a gross command area of 6800 ha, spread across nine villages
of three mandals (administrative units) of Karim Nagar district, Andhra Pradesh
(Ž gure 1) . The climate is semi-arid and the average annual rainfall of the study area
is 948 mm. Irrigation systems in the study area comprise canals, wells, dug-wells and
tanks. D-36 and D-36 A are the two distributaries commanding 1475 and 55.5 ha
respectively. The general localization pattern in SRSP is single wet crop in the D-36
distributary and single irrigation dry crops in the D-36A distributary. The major
crops grown are paddy, maize, turmeric, sugarcane, ground nut and other crops.
Red soils (sandy loam and sandy clay loam) are predominant covering an area of
about 65% of the total, while black soils (clay and silty clay) occupy about 35%
(SRSP-CADA 1980). The major physiographic units of the area are (i) granite hills
and inselbergs, (ii) granite hill foot slopes, and (iii) granite undulating plain. The
two generalized land systems of the study area are: (i) denudational (residual hills),
and (ii) pediments. Most of the study area is under pediments (lower pediments)
with slope range of 3–8%, moderately eroded with good to moderate groundwater
potential. The command area is underlain by archean group of rocks consisting of
granites and gneisses, metasediments of the purana group. The granites are mostly
exposed as sheets, boulders or domes. Groundwater occurs under water table condi-
tions in the weathered and fractured zones of granites. The saturated thickness of
the aquifer is 4–8 m. The thickness of the weathered zone varies from about 10 to
16 m. These weathered rock aquifers are developed through large diameter irrigation
dug wells, generally rectangular in shape.The depth of water levels vary from 2 to
11 m. The wells sustain continuous pumping of 2–3 h per day and yield varies from
90 to 120 m per day.
3
3. Agricultural crop land inventory
Geocoded FCC (NIR, red and green bands) imagery at 1:50 000 scale on three
dates: 28 October 1992 (path—row 144/ 047, Landsat-5 TM), 17 January and 29 May
1993 (Path-row 026—55, IRS 1B LISS-II) representing Kharif, Rabi and summer

Water balance and conjunctive water use planning
3229
Figure 1. Location map of the study area.
seasons, respectively, were visually interpreted to prepare a land cover map for each
season. The agricultural crop land is further divided into paddy land and non-paddy
land. Further, a distinction between various ID (irrigated dry) crops and the non-
paddy category could not be made from the visual interpretation techniques. The
study area is one of the typical command areas in the country and has a diversiŽ ed
cropping pattern (heterogeneously cropped).
Thorough examination of the digital data of the study area indicated that the
spectral signatures of the major ID crops are not separable. Hence, it was proposed

3230
V. V. Rao and A. K. Chakraborti
Figure 2. Temporal satellite data of the study area.
Figure 3. Land cover map (visually interpreted and rasterized image) of the study area during
kharif season, 1992.
to use a combination of visual interpretation and digital analysis of multi-temporal
satellite data consistent with the crop calendar in the study area to extract major
ID crops within non-paddy land cover category. Multi-temporal digital satellite data
of 8 July 1992, 28 October 1992, 29 November 1992, 17 February 1993, 6 April 1993,
8 May 1993 (Landsat-5 TM) and 17 January 1993 (IRS-1B, LISS II) were used

Water balance and conjunctive water use planning
3231
(Ž gure 2) to generate standard FCCs. Visually interpreted seasonal land cover maps
(Ž gure 3) were digitized and made compatible with the above-mentioned temporal
satellite digital data in terms of resolution of the picture element. The non-paddy
land cover category from the three digitized visually interpreted maps was extracted
by masking out other features. Then, these masked images were superimposed on
to the multi-temporal digital satellite data based on the season in which it fell. Thus,
non-paddy areas were transferred from visually interpreted seasonal maps to the
multi-temporal digital data and the rest of the features on FCC were masked.
Each of these digital datasets was classiŽ ed into cropped and non-cropped
(harvested Ž elds) for non-paddy areas using the Gaussian maximum likelihood
classiŽ cation algorithm. Then the results from all the multi-temporal digital data
were sequentially analysed consistent with the crop calendar for the major crops
grown in the study area to extract the extent of each major crop: maize, turmeric,
sugarcane, groundnut and others in each season. In this study, besides agricultural
crop information, remote sensing derived source-wise irrigated areas, land cover,
irrigation tank water spread, ayacut (area commanded by a tank) information, and
water yield estimates from the irrigation tanks (Rao and Chakraborti 1995) were
used together with the conventional Ž eld data as the inputs to estimate various
components of water balance and groundwater recharge.
4. Assessment of net groundwater recharge
The net regional recharge (R ) to groundwater during any time period is estimated
n
(Sondhi et al. 1989 ) by
Õ
R
R
Q
1
Q
(1)
5
n
g
g
p
where R
gross recharge to groundwater basin; Q groundwater in ow/out ow;
5
groundwater extraction through wells.
5
g
g
and Q
5
p
The gross recharge (R ) to the groundwater basin is given (Rao 1992) by
g
R
R
R
R
R
R
R R
(2)
5
1
1
1
1
1
1
g
e
c
d
t
ci
wi
ti
where R recharge due to rainfall; R recharge due to seepage from major distribu-
5
5
5
e
d
c
taries; R
recharge due to seepage from minor distributaries; R recharge due to
5
t
percolation from irrigation tanks; R
recharge due to percolation losses from canal
5
ci
recharge due to percolation from well irrigated areas;
irrigated areas; R
5
recharge due to percolation losses from tank irrigated areas.
wi
R
5
All the components in equation (2) were estimated by following the recommenda-
ti
tions of the groundwater estimation committee of the Ministry of Irrigation (1984),
with some modiŽ cations based on remote sensing derived command area inventory
and the Ž eld observed data. R , recharge due to rainfall, was estimated from the
e
daily rainfall records and the soil types and their extent in the command area. R
c
and R were estimated from the canal cross-sectional details, length of the canals,
number of days the canal operated, etc. R , percolation from irrigation tanks, was
estimated from the remote sensing derived irrigation tank water spread area and
d
t
utilizable water yield from irrigation tanks. While R and R were estimated using
the remote sensing derived source-wise irrigated area information as one of the
ci
ti
inputs, the R could not be estimated using remote sensing data. Since the area
estimates of various land covers and the tank irrigated areas compared very well
ti
(RD, relative deviation 4.1%) with the ground observed ACA (agricultural census
5
abstracts) Ž gures, the area irrigated by groundwater wells was estimated using the

3232
V. V. Rao and A. K. Chakraborti
proportion derived from the percentage contribution of various sources of irrigation
to the total irrigated area in ACA estimates. There are no groundwater wells present
in the tank irrigated areas in the study area. Details of estimation of each recharge
component are given by Rao and Chakraborti (1995). The speciŽ c percentage
allowances for the various recharge components (table 1) are as follows:
1. Recharge from rainfall (R ) is estimated as 12.5% of the annual rainfall
2. Recharge due to seepage losses from the major distributary at 3.5 m s
e
3
1
Õ
10 m , estimated to be 11% of water delivered
Õ
6
2
3. Recharge due to seepage from distributaries (R ) at 3.5 m s 10 m ,
2
Õ
3
1
6
Õ
d
estimated to be 9% of water delivered
4. Recharge due to percolation from irrigation tanks (R ) is 25% of live storage
capacity
t
5. Recharge due to seepage from canal irrigated areas (R ) of 35% of water
ci
delivered at the outlets is 6.39 Mm
3
6. Recharge due to seepage from well irrigated areas (R ) of 30% is 0.60 Mm
3
7. Recharge due to seepage from tank irrigated areas is 40%; as recommended
wi
by the groundwater estimates committee is 2.87 Mm
3
8. In addition to the above, seepage losses from paddy Ž elds contribute 3 mm
day for 120 days
Õ
1
Q is the volume of groundwater extracted in the year 1992–93 in equation (1),
estimated from well inventory data of the area, using average annual drafts for each
p
type of well operating in the region. The subsurface in ow or out ow of groundwater
across the aquifer boundaries (Q ) cannot be directly estimated. Hence, it is calculated
g
as the residue from the annual (crop year) water balance equation (Sondhi et al. 1989 ).
Ô
Ô
Ô
Ô
(P I) (ET
E
Q
Q Q
1
DS DS
DS )
(3)
1
5
1
1
g
s
p
s
m
g
where P precipitation over the region; I sum of irrigation water applied over the
5
5
region by the canal system (Q ), groundwater (Q ) and irrigation tank water (Q );
c
p
t
ET evapotranspiration; E soil evaporation from the uncultivated areas; Q
5
5
5
g
groundwater in ow/out ow; Q surface run-oŒ; DS
storage; DS change in surface water storage; and DS change in groundwater
change in soil moisture
5
5
s
m
5
5
s
g
storage.
All the above components are expressed in depth units (mm) for the area of
6800 ha. The methodology and data used are presented in the  ow chart (Ž gure 4).
Weighted rainfall estimated using the Thiessen polygon method assessing the daily
rainfall records of Ž ve rain gauge stations located in and around the area were used
Table 1. Gross recharge components to groundwater in the study area in 1992–93.
3
Recharge in Mm
Sl. no.
Sources of recharge
1
2
3
4
5
6
7
Recharge from rainfall (R )
5.18
1.73
1.25
1.91
6.39
2.87
6.01
e
Recharge from D-36 and D-36A major distributaries (R )
c
Recharge from minors (R )
d
Recharge from irrigation tanks (R )
t
Recharge from canal irrigated areas (R )
ci
ti
Recharge from tank irrigated areas (R )
Recharge from areas irrigated by wells (R
)
wi
Total
25.36

Water balance and conjunctive water use planning
3233
Figure 4. Methodology to estimate net groundwater recharge from the water balance study
using satellite data and ancillary data for conjunctive water use planning.
to estimate rainfall for the year 1992–93. Satellite remote sensing derived water yield
estimates (Rao and Chakraborti 1995) from irrigation tanks together with the
monthly canal releases at the oŒ-take point and groundwater extraction during
1992–93 were used to obtain I. For the annual water balance (for the crop year
May–June) both DS and DS may reasonably be assumed to be zero. However,
s
m
satellite imageries of 5 May 1992 and 8 May 1993 were digitally analysed to examine
the change in surface water body (irrigation tanks) spread areas. The areas were
found to be 27.4 ha in May 1992 and 27.1 ha in May 1993. The change in surface
storage (DS 0.3 ha) during 1992–93 is insigniŽ cant and, hence, assumed to be zero.
5
s
The DS under the semi-arid conditions that exist in the soils (predominantly sandy
loam) of the command area over prolonged dry spell conditions (during summer
m
months), is insigniŽ cant and can be assumed to be zero. The DS was calculated
g

3234
V. V. Rao and A. K. Chakraborti
from data of pre-monsoon (April/June) water levels recorded at nine observation
wells distributed over the study area. A value of 0.04 was used as speciŽ c yield
(Ministry of Irrigation 1984) for the granitic hard rock unconŽ ned aquifer of the area.
Evapotranspiration (ET ) was estimated from monthly data of potential evapo-
transpiration, and the area under various crops was estimated from the analysis of
temporal digital satellite data of the area consistent with the local crop calendar. A
distinction was made between evapotranspiration from irrigated and unirrigated
areas for each crop. It is presumed that the ET from the irrigated crop areas both
in monsoon and non-monsoon season occurs at potential rate. For the unirrigated
crops, ET is limited by the maximum available soil moisture at the beginning of the
season in the eŒective root zone of crops. Normally it is taken to be 80% of ET
(PET or ET
) from irrigated areas in the Kharif season and 60% of ET from
crop
irrigated areas in the Rabi season. Evaporation from uncultivated areas (E) was
calculated using Ritchie’s equation (Ritchie 1972).
E
ET t
(4)
5
1/2
Õ
0
where ET
in days.
the reference evapotranspiration; and t the time after the last rain
5
5
0
In the monsoon season, when the soil is frequently wetted, E is estimated to be
about 50% of ET by this formula. In other seasons it is about 25% (October–
0
February) and 10% (March–June) of ET . Since the stream  ow data is not available,
0
the surface run-oΠ(Q) in the study area was estimated using the USDA soil conserva-
tion service (SCS) model, which is a popular model to estimate surface run-oΠfrom
an ungauged agricultural watershed. Remote sensing derived land cover information
together with the basic soil information of the study area were used in IDRISI
GIS environment for estimating the area of each land cover in each one of the
hydrologic soils.
Since all the terms of the annual water balance equation except Q are known,
this quantity is determined as a residual of equation (3), as shown in table 2. The
g
net annual recharge and the corresponding water table rise (0.79 m) can therefore
be estimated using equations (1) and (2), as given in table 3. Comparison of the
model-estimated groundwater table rise with the observed water table rise (0.93 m)
during the year 1992–93 indicated in table 3 shows that the estimates of the water
Table 2. Estimates of water balance components during 1992–93 in the study area.
Sl. no.
Water balance component
Quantity (mm)
1
2
3
4
5
6
7
8
9
Rainfall (P)
622
229
233
133
1216
363
299
233
Canal supplies (Q )
c
Groundwater draft (Q )
Irrigation tank supplies (Q )
Total input
Evapotranspiration (ET )
Evaporation (E)
Pumpage (Q )
Change in groundwater storage ( S )*
Surface run-oΠ(Q )
Total output
w
t
w
Õ
D
32
g
10
11
12
175
1038
178
s
Groundwater out ow (Q )
g
Õ
*‘ ’ sign indicates falling groundwater table.

Water balance and conjunctive water use planning
3235
Table 3. Comparison of computed and observed water table in the study area.
Net
Gross
groundwater
recharge
Groundwater Groundwater groundwater
recharge
Eqivalent
fall in
water
Observed
outow
draft
water
table fall
(m)
(R )
in Mm
(Q )
in Mm
(Q )
in Mm
(R )
in Mm
g
p
g
n
3
3
3
3
table (m)
25.36
12.10
15.80
2.54
0.93
0.79
balance and net regional groundwater recharge are realistic. The validated model is
then used for predicting the groundwater table level under normal rainfall conditions.
5. Results and discussion
A systematic analysis of irrigation water demand in relation to available canal
supplies, groundwater and irrigation tank water was undertaken in the present study.
The overriding objective was to provide quantitative information on the current
operating practices and to suggest guidelines for improved water management in the
study area. This was done by comparing monthly and seasonal canal water availabil-
ity with the corresponding demand for water from CCA (Culturable Command
Area) of D-36 and D-36A distributaries and from the total cropped area, given in
Ž gure 5. The balancing role of groundwater as an additional resource and for
increasing the reliability of system operation was also examined. The analysis of
groundwater recharge and the water balance study were examined in this context to
investigate the scope for possible conjunctive water use in the study area.
Figure 5. Comparison of monthly irrigation water supply and demand in the study area
during 1992–93.

3236
V. V. Rao and A. K. Chakraborti
5.1. Status of water management and implications for conjunctive water use
The following are the observations from the supply–demand study (Rao and
Chakraborti 1995) conducted using satellite-derived command area inventory.
1. It was observed that the contribution to the total irrigated area from various
sources of irrigation, i.e. canals, wells and tanks was 40, 41 and 19%,
respectively, during the year 1992–93.
2. From the supply–demand study, it was observed that for the net sown area,
the total available irrigation water from all the sources was 39.04 Mm , whereas
3
the requirement was 41.74Mm , resulting in a deŽ cit of 2.7 Mm in 1992–93
3
3
(Ž gure 6). This emphasizes the need for the balancing role of groundwater in
conjunction with the proper regulation of canal  ows, so as to avoid surplus/
deŽ cit situations during various time periods (months) during the crop year
(1992–93).
3. The study revealed that the cropping pattern in the canal command area
showed a large deviation from the designed cropping pattern, eventually
leading to mismanagement of canal waters. This was re ected in the reduction
of the total area commanded by canals which was 820 ha in 1992–93, where
the designed command was 1512 ha. The impact of this deviation from the
designed cropping pattern was seen from the deŽ cits in the months of July
(1.73 Mm ) and April (0.54 Mm ), due to the large area under paddy crop,
3
3
although there was a surplus of 4.34 Mm in canal supplies as shown in Ž gure 5.
3
From the groundwater recharge study, it can be seen that the return irrigation
Figure 6. Comparison of total demand for irrigation water and available supplies during
1992–93.

Water balance and conjunctive water use planning
3237
from canal irrigated areas contributes 25% of gross recharge. Well and tank irrigated
areas contribute 24% and 11%, respectively. The contribution from rainfall is around
20%. The annual net groundwater recharge was found to be negative by 2.54 Mcm
resulting in a fall of the groundwater table by 0.79 m. In the event of normal rainfall
(rainfall during 1992–93 was 622 mm, which is 34% less than the average annual
rainfall), R at the rate 12.5% of annual rainfall will result in higher contribution
from it to gross recharge. Normalized values of the recharge estimates, obtained
e
from the water balance model, indicate that there will be around 1.0 Mcm net
recharge available as additional potential, which could cause the water table to rise
by 0.35 m.
Seepage losses from distributaries and minors are not only a function of canal
length and cross-section, but also of initial depth of the water table when seepage
begins. Lowering of water tables induces more seepage losses from canals, the canal
supplies are reduced and become less reliable as a result. Thus, it appears that the
twin objectives of conjunctive water use, namely, lowering the water table to control
waterlogging and augmenting the canal supplies, while increasing their reliability,
are incompatible. This is so unless at least two additional factors are included. The
Ž rst is the operating depth of the water table, which is the primary design variable.
This value depends on the irrigation system, soils, subsurface conditions, crops grown
and other related parameters. The second signiŽ cant factor is that canals and aquifers
must be operated rotationally in diŒerent time periods. The rotational periods will
be unequal and will vary with irrigation system and aquifer conditions. The operation
of surface and groundwater systems in successive periods leads to increased
storage (increased  ows in canals) in both surface and subsurface reservoirs and to
improvements in overall water use e ciency.
From the groundwater budgeting and supply–demand study, the following rota-
tional cycle of conjunctive water use is suggested in the study area. Figure 5 shows
that there is a large deŽ cit in the month of July, which is due to non-adherence to
the design cropping pattern. Hence, the original cropping pattern envisaged in the
design is to be restored so that a large area can be brought under irrigation (under
ID crops) and to meet the overall deŽ cit of 2.7 Mm in 1992–93. The aquifers are to
3
be pumped to a pre-deŽ ned limit (between 3 and 6 m is suggested based on historical
well inventory data of the study area), at this stage to lower the water table and to
meet the transplanting requirement of paddy in the month before operating the
canals. A large part of the water requirement in this month can be met by the
monsoon rainfall besides groundwater. Then, the canals should be run for 40–50
days, to once again raise the water levels, which will be lowered in the next cycle by
abstraction from the aquifer. This also meets the high requirement during the months
of September–October in the study area. This cycle can be repeated to meet excess
demand in December during Rabi paddy transplantation. Since the study area readily
responds from return irrigation, this rotational cycle of conjunctive water use will
not only eliminate intra-seasonal imbalances in supply–demand in the study area,
but also lead to additional development of groundwater potential which will ensure
improved water management and bring more area under assured irrigation.
6. Conclusions
In this study an attempt is made to use the remote sensing derived command
area inventory, i.e. various land cover categories, paddy and non-paddy crop land,
major irrigated dry crops under the non-paddy crop category, irrigation tank water

3238
Water balance and conjunctive water use planning
spread information along with their irrigated areas, used in conjunction with the
Ž eld observed ancillary data in developing a semi-empirical water balance model for
the study area. The model was successfully validated in a typical heterogeneously
cropped irrigation command area. Water budgeting of the study area during 1992–93
indicated that the net recharge to the aquifer is negative by 2.54 Mcm resulting in a
fall of the groundwater table by 0.79 m. The validated water balance model was used
to predict the groundwater levels under normal rainfall conditions. It was found that
the groundwater table would rise by 0.35 m per year indicating impending waterlog-
ging conditions in the study area. Since the design of conjunctive water use schemes
in irrigation projects needs to be based on an understanding of the complex inter-
actions between the surface water and groundwater systems of the area, a further
similar study is to be conducted in at least 3–4 years to draw up more realistic
conjunctive water use strategies in the study area. The present study also provides
scope for better representation of various components that are involved in re-
charge and water balance studies. Though the study requires further reŽ nement, it
holds promise for better parametrization of various variables that are involved in
groundwater targeting.
Acknowledgments
The authors are extremely thankful to Professor B. L. Deekshatulu, then Director
of the National Remote Sensing Agency (NRSA), Hyderabad, for providing an
opportunity to conduct this study under the technology development programme.
The study was conducted with the active support and guidance of Professor
S. K. Bhan, Dean of the Indian Institute of Remote Sensing (IIRS), Dehradun.
References
Government of India, 1985, Seventh Five Year Plan, 1985–90, Vol. II (New Delhi: Planning
Commission, Government of India).
Ministry of Irrigation, 1984, Report of the Groundwater Estimation Committee—
Groundwater Estimation Methodology, Government of India, New Delhi.
Rao, V. V., 1992, Studies on water management in irigation canal command area—a case
study. phD thesis, IARI, New Delhi.
Rao, V. V., and Chakraborti, A. K.,1995, Development of methodology for assessment of
water resources and conjunctive water use planning in irrigation command areas using
satellite remote sensing data. Technology Development Project Report, Water
Resources Division, IIRS, Dehradun, India.
Ritchie, J. T., 1972, A model for predicting evaporation from a row crop with incomplete
cover. Journal of Water Resources, 8, 1204–1213.
Sondhi, S. K., Rao, N. H., and Sarma, P. B. S., 1989, Assessment of groundwater potential
for conjunctive water use in a large irrigation project in India. Journal of Hydrology,
107, 283–295.
SRSP-CADA, 1980, Regional soil and water management pilot project report. Jagityal,
SriRamSagar Project Command Area Development Authority, Karimnagar district,
Andhra Pradesh, India.