Climate change and extreme variability threaten food security in many regions worldwide. In addition, demands on limited water supplies for food production often are in sharp conflict with other needs. Strategic placement and area-wide evaluation of water conservation zones such as riparian areas, wetlands and ponds in agricultural catchments can be suitable options to store freshwater for biomass production, water quality and food security. Availability of additional freshwater in the catchments can provide opportunities for multiple uses, including livestock and aquaculture. In addition, these water conservation strategies can also improve water quality through various biogeochemical processes to filter agricultural pollutants including both nutrients and sediments. At present, there is a lack of understanding of the linkage between land use activities and the functions of these water conservation systems. Activities and hydrological processes occurring in the upper catchment often affect downstream water storage and nutrient availability. Area-wide knowledge on the sources and sinks of water such as the magnitude, frequency, duration, timing, and rate of the water flow regimes, and nutrient and their cycling into and out of the system as influenced by upland activities is therefore needed to underpin the selection of sustainable management practices of these systems for conservation and reuse of water and nutrients.
To improve water management for agriculture and downstream water quality using water conservation zones (farm ponds, wetlands and riparian buffer zones) in agricultural catchments
To maximise the use of water conservation zones for crop production
To optimize water and nutrient capture and storage in water conservation zones for downstream irrigation use
To regulate water and nutrient cycling in water conservation zones to improve biomass production and downstream water quality.
(1) In Tunisia, a farm pond occupying approximately 3% of the catchment area (272 ha) was able to capture surface runoff and subsurface water (up to 140,000 m3) and associated nitrogen (up to 280 kg) generated in from the catchment. The captured is water and nitrogen are used for growing high value vegetable crops of (6 tonnes per /ha) per year and potentially reduce the nitrogen contamination of downstream water by 90%.
(2) In Iran, 30 surface ponds (Ab-bandans) in the Caspian lowlands occupying approximately 3% of the catchment area (10,400 ha) was able to capture 7 million m3 of water together with of 86 tonnes N and 17 tonnes of phosphorus. This water along with nutrients helped to increase irrigation area from 730 to 1,500 ha and rice production from 2,560 to 5,050 tonnes
(3) In Northeast China wetlands can be used to cultivate 10 tonnes/ha of rice without contaminating surface and ground water by nitrate through optimizing water conservation in these rice wetlands.
(4) Wetlands in the Manafwa catchment, Uganda was able to remove 64 tonnes of N (70%) from the incoming river water in a single growing season and used for rice production providing a net economic return of US$1,300 per ha per cropping season.
(5) The riparian buffer zones with alder trees used for fuel wood remove between 170 and 350 kg N/ha/year and reduce nitrate contamination of downstream water by 50%. Most of this removal was accompanied by denitrification to N2 gas thus reducing greenhouse gas emission to the atmosphere.
(5) The capacity of participating institution on the use and application of isotopic and nuclear techniques has been enhanced as results of this project. This include nitrogen-15, oxygen-18 and hydrogen-2
The CRP provided very useful data and information on sources and pathways of water and nutrients that can help develop guidelines for designing and managing water conservation zones in agricultural catchments. A guidelines for designing and operating wetlands for optimizing the performance is currently under preparation and will be completed by the end of 2015.