Transcript Water Productivity: Potential for Improvements

Water Productivity in Agriculture:
Potential for Improvements
Madar Samad, B. R. Sharma, K. Palanisami and M.
Dinesh Kumar
with
OP Singh, Malkit Singh and Chaitali Purohit
Objectives of the Research
The Overall Objective: To analyze the potential for improving
the water productivity at different river basins. The specific
objectives are:
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Opportunities and constraints for improving dry land/rain-fed
agriculture
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Potential of spreading water saving technologies
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Potential and pitfall of rainwater harvesting and decentralized
recharge and
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Institutional and policy mechanisms and the implications of the
growth scenarios on water demand drivers.
Objective I: Opportunities and Constraints for
improving rain-fed/dry-land agriculture
Hypothesis:
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For purely rain-fed crops in sufficiently high rainfall areas, proper
nutrient management can help enhance yield and water
productivity
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For dry-land crops, supplementary irrigation and nutrient can
help enhance not only yield but also water productivity
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Better reliability and adequacy of irrigation can improve yield
and water productivity of irrigated crops through better
agronomic practices and better water management
Methodology for Analyzing Productivity of
Crops with Supplementary Irrigation
The combined water productivity for rain-fed crops with
supplementary irrigation would be estimated as:
Average Net Economic Return of crop “k”/ {[ETk - ∆k max] +
∆k average}
Here, ∆k max will be the maximum irrigation applied for a
crop. For paddy, the crop water requirement instead of
consumptive use (ET) is considered.
Marginal Productivity: Multiple regressions to estimate the
differential impact of irrigation and other inputs on combined
water productivity. From this, the impact of irrigation and
fertilizer inputs on water productivity could be analyzed.
Methodology for Analyzing Water Productivity
of Irrigated Crops
Farm level water productivity of crop i and farmer j = Yield or
Net Return (C ii)/ (∆ ij)
System level water productivity of crop i and farmer j=Yield or
Net return ((C ii)/ (ETi)
This is when ∆ ij > ETi; and groundwater table is shallow.
When the groundwater is deep or saline, then total applied
water would be considered in the denominator for water
productivity.
But if ∆ ij < ETi then system level water productivity would be
based on the applied water.
If system level water productivity is higher than the farm level
water productivity, it means that on farm water management
can improve agricultural water management.
Locations Studied
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Sabarmati River Basin in Gujarat--21,676 sq.
km
Bhawani river basin in Tamil Nadu
Narmada River Basin in Madhya Pradesh-1,00,000 sq. km
Bist Doab Area in Punjab in Indus Basin-10,000 sq. km
Progress
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Field studies completed in Sabarmati river basin--6
locations (agro-climatic sub-zones)
Field studies completed in Narmada river basin-9 locations
and seven agro-climatic sub—zones
Analysis of average water productivity (spatial, and also
crop-wise completed; marginal productivity to be done
Field studies completed and initial analysis and draft paper
ready for Palar basin--Climate?
Field studies almost completed in Bist Doab area in Punjab-Two agro climatic zones
Issues being investigated
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Analyzing impact of water control on WP:
Comparative average water productivity in conjunctive
use and well irrigation and also marginal productivity
in both (Punjab; Sabarmati)
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Analyzing impact of water allocation on water
productivity through: 1] comparing green water
productivity and combined water productivity in dry
land crops; 2] analyzing marginal water productivity
of applied water in irrigated crops with irrigation and
fertilizer inputs (all basins)
Impact of climatic variations on WP:
 spatial analysis of water productivity (Sabarmati;
Narmada; Indus; Bhawani)
 District-wise estimates of average WP of major crops
Some results from Bhawani basin work
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Water control has impact on water productivity: well
irrigated crop has higher physical productivity and
economic efficiency in paddy as compared to those
irrigated by system and non-system tanks & canals
Functional analysis of paddy yield shows highest impact of
water input on yield, followed by fertilizer and labour
Water productivity in fish and floriculture was also
estimated and economic efficiency much higher in these
crops.
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Marginal productivity analysis is to be done
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Studies to be done for different climates
Scope of Water Saving Technologies in Water
Productivity Improvements
Basic Premise: There are several constraints in the
adoption of water-saving irrigation technologies,
while there are opportunities for real or “wet”
water saving through technology adoption.
The constraints are due to:
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Source-wise irrigated area in different agro-ecological
regions; the existing irrigated cropping patterns and
systems; power supply restrictions
There are opportunities for water-saving through yield
enhancing as well as ET reducing crop technologies
Methodology
The study is based on analysis of secondary data on cropping
pattern in some typical river basins; and the data available
from both field-based and laboratory research on the impact
of WSTs on “applied water” and consumptive use (ET) in
conventional irrigation and micro irrigation systems.
The study involves extensive literature review to find out the
physical impact of water-saving irrigation and crop
technologies on yield, crop consumptive use and “depleted
water” in irrigation.
Analytical Procedures
The total water saved through water saving technologies = Ai* [WDi
–WDi micro].
trad
Where “i” varies from 1 to n; “n” is the number of crops for which MI
systems can be used.
In the case of traditional irrigation method, water depleted per unit area
(WDi trad) is estimated as =
Total Volume of water applied per unit cropped area + Soil Moisture
Depletion in Root Zone – Recharge to Groundwater per unit area.
In the case of micro irrigation, the Total Water Depleted per unit area
(WDi micro) is estimated as =
Total Volume of water applied per unit cropped area + Soil Moisture
Depletion in Root zone. Realistic estimates of “recharge to
groundwater” would be arrived at using data from past research for
various irrigated crops on soil and groundwater balance.
Progress so far
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Extensive review of literature on water saving irrigation
devices and their potential impacts on water use, yield
Review of literature on the return flows from
conventionally irrigated fields
Analysis of primary data from research station for watersaving and yield impacts of irrigation devices--different
types of drips & sprinklers and plastic mulching for
different crops (groundnut, potato, alfalfa, castor etc.)
completed
Analysis of data on irrigated cropping pattern (sourcewise) in different agro-ecological regions of India
completed
Water Harvesting: Potentials and Pitfalls
Hypothesis
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In regions where rainfall and runoff are excessively
high, and system losses are low (low ET and E),
potential for water harvesting is high; but demand
for water is low due to poor access to arable land
and low PET/Rainfall ratios.
In regions where rainfall and runoff are low; and
system losses such as ET and E, the potential for
additional water supplies would be low, while the
demand for water would be quite high due to large
arable land, high PET/rainfall ratios.
Hypothesis: Continued
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Many basins in water scarce regions are “closed”.
Hence, increasing water harvesting increases only
helps reallocation of water rather than adding to the
overall hydrological balance.
In many basins, the upper catchments are water-rich
than lower catchments. But water demands are higher
in lower catchments.
But, allocation of water harvested through small water
harvesting might contribute to improved water use
efficiency in irrigated crops
Approach
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The approach is eclectic involving analysis of
secondary data on macro hydrology of selected
river basins covering water-rich and waterscarce ones; hydrological monitoring and
simulations for selected sub-basins/watersheds;
and primary data collection using social science
research methods.
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Analysis of macro hydrology of India
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Micro level hydrological monitoring
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Farmer surveys in intensive water harvesting
areas covering beneficiaries and nonbeneficiaries
Objectives of Field Research
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Analyze the trade off between local and basin level
impacts of small water harvesting interventions vis-àvis hydrological benefits
Examining the impact on local groundwater regime
Impact of water harvesting on surplus value product
from a unit of water diverted for irrigation
(supplementary or otherwise)
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Through improvement in WUE (physical)
Through reduction in irrigation costs
Comparing the net surplus value product in crops
irrigated through harvested water and crops irrigated
with the surplus water in the downstream area
Locations for Field Study
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Arawari basin in Alwar, Rajasthan
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Paupogni catchment of Krishna basin
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Full of small and large tanks, water used for
irrigation, cattle
Kundi basin of Narmada in MP in Narmada
valley
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Full of Johads and anicuts, water for cattle main
Full of small water harvesting structures, no direct
use of water for any purpose (recharge and soil
moisture conservation
Galo basin in Saurashtra in Gujarat
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Full of check dams (recharge and surface storage)
Progress made so far
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Kundi basin study completed--draft ready
Hydrological data gathering and groundwater monitoring
completed in the rest three basins
Hydrological analysis completed for Galo—runoff
estimation, simulations using US Curve number method
Mapping of water harvesting structures completed in the
four basins completed using GPS
Remote sensing imageries of the basins obtained and
mapping being done
Analysis of macro hydrology completed
Outputs expected by March
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Synthesis report on water harvesting based
on four location studies
Papers on water productivity in irrigated
agriculture (two at least)
Paper on water saving technologies