ZEF Bonn

56
ZEF Bonn ● Center for Development Research – Annual Report 2001/2002
The ways in which soil,
nutrient, or organic matter losses
occur, and the mechanisms
involved in restoring these losses,
need to be understood if
sound policies are to be devised
to maintain soil fertility.
ZEF projects can lead to
management options that
avoid or reverse them.
The ultimate goal of improved water management is to enhance human welfare in a
manner that is sustainable and does not damage the environment. Water resources
for agriculture in Asia are becoming increasingly scarce, and ways must be sought to
optimise the use and efficiency of irrigation systems. More than 75 % of the world's
rice supply comes from 79 million ha of irrigated land in Asia. Irrigated agriculture
accounts for 90 % of total diverted freshwater, and more than 50 % of this is used
to irrigate rice in Asia. However, irrigated rice is a heavy consumer of water: it takes
some 5,000 litres of water to produce a single kilogram of rice. More than half the
water consumed in rice production is used to prepare the land, and most of this is
lost in the process through non-beneficial use of evapotranspiration, seepage and
percolation. There is an urgent need to develop management policies for efficient
operation of irrigation systems, technologies that reduce water consumption, changes
in rice crop management to increase water productivity and provide economic
incentives to farmers to reduce water losses. ZEF is tackling this issue in a project on
“Water Accounting and Productivity at Different Spatial Scales in a Rice Irrigation
System; A Remote Sensing Approach". The objectives of this study, which is being
conducted at the International Rice Research Institute (IRRI) in the Philippines, are:
● to estimate actual evapotranspiration using different public sensors like Landsat
7 ETM+, TERRA/ASTER and TERRA/MODIS data at different spatial and temporal
scales within the district of the Upper Pumpanga River Integrated
Irrigation System (UPRIIS) Philippines,
● to develop methods for evaluating water use efficiency at 6 different spatial
scales in the system and
● to measure water productivity at 6 different scales within District 1 of UPRIIS.
UPRIIS covers roughly 25,000 ha and is bounded by the Talavera and Ilog Baliwag
rivers on both sides. The most common land use in this district is double cropping
of rice through the transplanting method. The climate in UPRIIS is characterised by
two pronounced seasons, a dry one from November to April with an average rainfall
of 170 mm and a wet one from May to October with an average rainfall of 1,730
mm. The water balance for an irrigation project is a complex set of inflows, outflows,
consumptive use, and recycling of water. This is why 200 points were monitored
twice for measuring inflow and outflow at different scales from the irrigation
system for two cropping season in 2000 and 2001. A comprehensive field campaign
was carried out to measure re-use of water from groundwater, creeks, seepage and
percolation along different soils, involving groundwater table monitoring, setting up
a network of rain gauges and a social survey of 60 farmers in the district. Water
balancing is calculated at six different spatial scale levels to test the hypothesis that
water-use efficiency and productivity increases with increasing scale level because of
increasing options for water re-use.
3.2 Sustainable Land Use System
ZEF's research includes the global issues of soil degradation, soil erosion, and broken
nutrient cycles linked to development processes. These problems and their causeand-effect
relationships are often regional in character. The ways in which soil,
nutrient, or organic matter losses occur, and the mechanisms involved in restoring
these losses, need to be understood if sound policies are to be devised to maintain
the soil fertility. Here, ZEF's projects seek to increase understanding of degradation
processes and aim at management options that avoid or reverse them.