Where Water Meets Earth
Where Water Meets Earth: A Visual Journey of Watershed Delineation
Watershed delineation is the process of identifying and mapping the boundaries of a watershed, which is an area of land where all the surface water drains into a common outlet, such as a river, lake, or ocean. The concept is based on the natural topography of the land, where water flows downhill from higher elevations to lower elevations.
Watershed delineation steps
Digital Elevation Model (DEM) acquisition: A DEM is a digital representation of the elevation of the Earth's surface. It is used to understand the topography of the area and identify the flow of water across the landscape.
Flow direction determination: Using the DEM, the direction in which water flows across the landscape is calculated. This is based on the principle that water flows perpendicular to the steepest slope.
Flow accumulation: The flow accumulation process calculates the accumulated upstream flow in each cell of the DEM. This information helps identify potential flow paths and stream networks.
Watershed boundary identification: Starting from a specific point (usually the outlet or mouth of the watershed), the boundaries of the watershed are determined by tracing back the flow accumulation cells until the entire contributing area is encompassed. These are the areas where all the water converges to the same outlet point.
Watershed delineation refinement: The initial delineation may require refinement to account for factors such as lakes, reservoirs, or man-made structures that can alter the natural flow of water.
Watershed delineation is essential for various environmental management and planning activities, including flood risk assessment, water quality monitoring, erosion control, and land use planning. It allows us to understand the hydrological processes within a specific geographic area and provides valuable information for sustainable water resource management. Various Geographic Information System (GIS) software tools and hydrological models are commonly used for this purpose.
Watershed Delineation using archydro in arcgis pro
ArcHydro is a set of tools and data models designed for water resources analysis and hydrological modeling within the ArcGIS environment. It is an extension that works with ArcGIS Desktop, including ArcMap and ArcGIS Pro. ArcHydro provides a comprehensive suite of tools to support various hydrological tasks, such as watershed delineation, flow direction and accumulation, stream network creation, and more.
The following video walks you through different steps of watershed delineation:
Steps to perform point delineation explained in the video:
01:31 - 2:52 How to download ArcHydro for ArcGIS Pro
2:52 - 05:16 Fill Sinks
05:16 - 06:36 Flow Direction
06:36 - 07:54 Flow Accumulation
07:54 - 10:03 Stream Definition
10:03 - 11:00 Stream Segmentation
11:00 - 12:17 Catchment Definition
12:17 - 13:12 Catchment Polygon Processing
13:12 - 15:07 Drainage Line Processing
15:07 - 16:02 Adjoint Catchment Processing
16:02 - 19:05 Create Outlet Point
19:05 - 21:31 Point Delineator