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Quantification of Hydrological Fluxes in Irrigated Lands Using Isotopes for Improved Water Use Efficiency
Closed for proposals
Project Type
Project Code
F32005CRP
1429Approved Date
Status
Start Date
Expected End Date
Completed Date
11 January 2013Objectives
The overall objective is to enhance the application of water use efficiency techniques in irrigated lands at the field and basin scales in Member States. The objective will be met through development and implementation of isotope methods for quantification of two of the major fluxes (deep percolation and evaporation) that control the water balance of irrigated lands, and therefore, are a measure of the degree of water use efficiency. The specific objectives are (1) at the farmer’s field scale, quantify spatial and temporal distribution of deep percolation and evaporation in irrigated areas within selected basins; and (2) at the basin scale, assess the relative importance of sources of deep percolation and evaporation losses (e.g. non-irrigated lands versus irrigated fields) within specific basins.
Specific objectives
At the basin scale, assess the relative importance of sources of deep percolation and evaporation losses (e.g. canals versus fields) in irrigation basins
At the field scale, quantify spatial and temporal distribution of deep percolation and evaporation in irrigated areas within selected basins
Impact
The CRP results were sufficient to clearly indicate the large effect of irrigation practices on water use efficiency. Some studies showed deep drainage pulses that occurred after irrigation events that have no benefit to the crops and could potentially transport fertilizers and other contaminants to groundwater. Such pulses can also contribute to water logging through rising groundwater tables. The isotope results also indicate issues related to evaporation losses which also lower water use efficiency from the crop perspective.
In terms of capacity building the CRP has been very successful. Five MSc theses were completed (Austria (1), Israel (1), and the Netherlands (3)), and two PhD studies were completed in China and Tunisia as part of the CRP.
Relevance
The field studies carried out under the CRP highlighted the importance of temporal variations in the intensity of water input into crop fields for the development of deep percolation. This aspect is important to assess the efficiency of water use in crops, as well as natural rain-fed ecosystems and the possible impact in groundwater quality. In order to properly assess these aspects, it is recommended to have a good sampling setup to capture the temporal variability of all involved water cycle components by increasing the frequency of sampling. It is also important to have a clear understanding of the involved water components and their isotopic composition. This includes the accurate estimation of end members like irrigation water, precipitation, soil water, percolation and the atmospheric components.
The CRP showed the contribution that isotope tools can provide to better characterize and assess hydrological processes in the soil/root zone, the unsaturated zone and the water table, covering a wide ranges of issues, such as the quantification of water use efficiency or the impact of certain agriculture practices on groundwater quality.