GenRiver and FlowPer: Generic River Flow Persistence Models - user manual version 2.0

Water flow in rivers is generated by rainfall and modified by landscape topography, vegetation and soil and also by human engineering to enhance drainage and/or retention of water. The degree to which river flow is influenced by land-cover change (deforestation, reforestation, agroforestation and other such practices) is hotly debated, as is the influence of climate change. A simple tool that relates plot-level to river-level consequences was deemed relevant to assist in the analysis of catchment data. Existing models were either too complex and data-hungry or left out important processes, such as the impact of land-use change on the soil and its physical condition. GenRiver is a generic river flow model that responds to spatially explicit rainfall and keeps track of a plot-level water balance that responds to changes in vegetation and soil. The model treats a river as a summation of streams, each originating in a subcatchment with its own daily rainfall, yearly land cover fractions and routing time based on distance to the river outflow (or measurement) point. Interactions between streams in their contribution to the river are considered to be negligible (that is, there is no “backflow” problem). Spatial patterns in daily rainfall events are translated into average daily rainfall in each subcatchment in a separate module (SpatRain). The subcatchment model represents interception, infiltration into soil, rapid percolation into subsoil, surface flow of water and rapid lateral subsurface flow into streams with parameters that can vary between land-cover classes. GenRiver was first developed as part of an Australian Centre for International Agricultural Research-funded project on watershed functions in landscape mosaics. This manual is reproduced through the TUL-SEA (Trees in Multi-Use Landscapes in Southeast Asia) project, funded by the German Federal Ministry of Economic Cooperation and Development (BMZ) and Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ). However, these sponsors are not responsible for any of the information provided in this manual. The authors wish to acknowledge many colleagues and users for their valuable contributions and advice

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