Linkages between rice, land, and water in rice landscapes of upland Lao PDR: An agroecosystem and integrated hydrologic modeling analysis

Populations in mountainous northern Lao PDR are dependent upon rice production for sustenance and livelihoods. Rice is grown in two distinct agroecosystems in upland Laos: upland rice cultivated on hillslopes within traditional shifting cultivation systems, and montane paddy rice grown on bunded fields. Unsustainable cropping intensities on the hillslopes have led to a serious and rapid decline in system productivity. One potential alternative is to intensify paddy rice production to maintain rice sufficiency while relieving cropping pressure on fragile slopes, requiring an assessment of how land use changes on the slopes affect water availability, the primary constraint to paddy rice production. This research adopts a "rice landscape" approach (1) by performing a qualitative assessment of rice-water interactions using agroecosystem analysis to place rice production and water flows within the context of the overall system, and (2) by implementing an integrated watershed hydrology model to an upper catchment in northern Laos to assess water availability response to alternative land use regimes. Agroecosystem analysis utilized participatory assessments and resource mapping to derive linkages between rice production and water flows. This approach aids in delineating a typology of montane paddies with differing hydrologic implications, and helps identify potential paddy expansion strategies. Land use and water flow characterization methodology, model development, and calibration/validation outcomes are presented for the hydrologic analysis, as well as assessments of alternative land use scenarios. Modeling results suggest that conversion of intensive shifting cultivation systems to less-intensive land uses may increase water availability for paddy irrigation in the early wet season, but that dry season paddy viability is relatively unaffected. Losses in upland rice production from land conversion can likely not be compensated with paddy expansion without simultaneous yield increases from paddy intensification. Land use mosaics affect water availability in addition to total areas under each land use, i.e. high fragmentation of swidden areas has a positive effect on paddy water availability. However, modeling results are sensitive to hydrologic characterization and parameterization of forest and fallow areas, land uses which are not well-understood. Subsequent implications for results and areas for further research are discussed.