Agriculture Reference
In-Depth Information
000 to 84 000, making it difficult for the government to collect revenue
through the metering system (Qureshi and Akhtar, 2003). Increased elec-
tricity prices and unannounced power cuts resulted in the stagnation of
electric tubewells and an increase in diesel tubewells. Although the cost of
water from diesel tubewells (2.20 US¢ m
−3
) was still higher than electric
tubewells (0.70 US¢ m
−3
), diesel tubewells were preferred due to low ini-
tial installation and operational costs.
The latest estimates suggest that in 2010, farmers extracted 50 bil-
lion cubic metres (BCM) of groundwater through 1.2 million diesel and
electric tubewells (Qureshi et al., 2010). Of this, about 0.8 million are
located in Punjab. About 200 000 tubewells are operated by electric mo-
tors whereas the remaining 1 million are run by diesel engines of various
capacities. Out of a total 50 BCM of groundwater extraction, about 12
BCM is extracted using electric pumps and the remaining 38 BCM using
diesel pumps.
The depth to groundwater is directly linked to energy requirements
for water extraction. In a countrywide survey of 1200 private tubewells,
Qureshi et al. (2003) found that in Pakistan, electric tubewells are used to
extract water from greater depths (40-80 m) and diesel tubewells are used
for shallow water table areas (6.0-15 m). The farmers use pumps which
are not energy-effi cient due to low capital investment. Due to high friction
losses in wells and ineffi cient water conveyance systems, energy losses are
very high. Energy requirements for extracting groundwater are highly sen-
sitive to the dynamic head over which the groundwater is lifted. Therefore
for energy calculations for this paper, a conservative estimate of dynamic
head for electric and diesel pumps has been taken. For electric tubewells,
a dynamic head of 60 m is assumed. For diesel pumps, a dynamic head of
10-15 m is considered because beyond this depth diesel pumps become
extremely ineffi cient, forcing irrigators to switch to electricity. Therefore
for diesel pumps, operational hours are more important for energy require-
ment calculations than dynamic head.
Electricity consumption in groundwater irrigation can be calculated
based on the energy requirement to lift the water. To lift 1000 m
3
water
from 1-m depth at 100% effi ciency (without considering friction losses),
2.73 kWh of energy are required (Karimi et al., 2012). Thus energy con-
sumption can be calculated as follows:
