Mapping of the historical extent of irrigation
Irrigated agriculture has significant impacts on the global water cycle. It increases evapotranspiration on agricultural land and reduces stream flow. Irrigation also has a significant cooling effect on surface temperature. The main reason why farmers use irrigation is to compensate for missing precipitation and soil moisture to increase crop yields. This also allows an efficient use of additional inputs like fertilizers. As a consequence crop yields are on average larger on irrigated fields compared to rain-fed agriculture.
While more and more information on the actual extent of irrigated agriculture has become available within the last decade and while the quality of the derived data products has been increasing significantly, information on the historical extent of irrigation is still very rare. Such information is required in particular for modelling slow changing systems like the global climate system, the global water cycle or decomposition processes in the soil. The models used here are often applied for periods lasting several decades or even centuries. A spatial data set showing the historical extent of irrigation is therefore requested to avoid simple ad-hoc assumptions for the historical irrigation extent.
The objective of the project is to develop time series of data layers indicating area equipped for irrigation back to year 1900 by combining 1) the most recent version of the Global Map of Irrigation Areas, 2) national and sub-national historical irrigation statistics and 3) historical maps indicating location and extent of the major irrigation areas in former times. Data sets developed in the scope of this project as well as related documentation reports are made available for download on the web page of the project.
Keywords: irrigation, database, global map, land cover, land use, water use, agriculture, hydrology, history
Participants: Stefan Siebert, Petra Döll
Cooperating institutions: Department of Geography, McGill University, Montreal, Canada and Bureau of Economic Geology, University of Texas, Austin, US
Duration: since 2006 (ongoing)
Funding entity: state funds
Contact: hydrology@em.uni-frankfurt.de
