Where_does_water_come_from

Where does water come from and how is it routed through the watershed? It is critical to know the sources (snow melt, rain, ground water) of water, and the routes that it takes before reaching the point(s) of water supply intake. Knowing this allows the identification of those who could benefit from water security, identification of sources of alterations to water quality and quantity, evaluation of the types and degrees of alterations, and an evaluation of the potential for different activities to address those alterations. It also allows analyses of land ownership and potential for engaging in actions that would be implemented in the watershed. The following questions are asked in an initial evaluation of the watershed: • Is the water collected from more than one watershed or aquifer? • What are the boundaries of the watershed(s) or aquifer(s)? • Where does the water come from - is surface water, groundwater or a mix between the two the main source(s) of water in the watershed(s)? • Is surface water in the watershed(s) from glaciers, snow melt and/or rain? • Where in the stream network(s) is (are) water intake(s) located for municipal, industrial, local community and irrigation water supply? • If there is more than one intake in a given watershed, or water is provided from more than one watershed, what are the proportionate amounts of water they provide? To understand where water comes from and how it is routed on the surface throughout the watershed, you will need to have access to a map of the watershed(s) and streams, lakes, and wetlands, or may need to create one using automated GIS routines that are based on a digital elevation model (DEM) and the location of your water resource access points. Both DEM data and GIS software are needed to develop these products, and to perform analyses described later. GIS data to represent watersheds, stream routes, flow directionality, and other attributes are available globally through HydroSHEDS. Spatial data on glaciers can be attained from the Global Land Ice Measurements from Space (GLIMS). Note: Regional data may provide more accurate data on streams, and more accurate and comprehensive data on glaciers. For groundwater, the starting point is to understand the characteristics of the aquifer of interest in terms of type (confined or unconfined) at the depths of interest based on the geo-hydrological information available. This will vary from aquifer to aquifer. The objective here is to understand how recharge is occurring at a depth of interest and then to identify the surface area contributing to the water infiltration process that is initiating the recharge process. Information on aquifers is not global, so local and regional data sources should be investigated. Intake points for municipal, industrial, local community and irrigation water supply locations, water transfer locations, reservoirs, and other water infrastructure will probably require local and regional sources of data and expert input to identify where in the stream network these are located. These provide a clear picture of the potential water user