ArcGIS | ArcMap | Hydrological modeling in | Mapping in GIS
Hydrological modeling in ArcMap 10.8
A hydrological model is an input–output model that simulates the evolution of water storage, water fluxes, and potentially associated chemical and physical properties at the Earth's surface and subsurface, based on the water balance equation
Hydrology plays a central role in applied and fundamental environmental sciences, but it is well known to suffer from an overwhelming diversity of models, particularly to simulate streamflow. We discuss here in detail how such diversity did arise based on the example of Switzerland. The case study's relevance stems from the fact that Switzerland, despite being a small country, shows a variety of hydro-climatological regimes, of water resources management challenges, and of hydrological research institutes that led to a model diversification that stands exemplary for the diversification that arose also at larger scales. Our analysis, based on literature review, personal inquiry, and an author survey, summarizes the main driving forces behind model diversification. We anticipate that this review not only helps researchers from other fields but in particular also the international hydrology community to understand why we have so many different streamflow models.
The hydrologic modeling tools in the ArcGIS Spatial Analyst extension toolbox provide methods for describing the physical components of a surface. The hydrologic tools allow you to identify sinks, determine flow direction, calculate flow accumulation, delineate watersheds, and create stream networks.
Using an elevation raster or digital elevation model (DEM) as input, it is possible to automatically delineate a drainage system and quantify the characteristics of the system.
The DEM on which the hydrologic analysis will be performed.
Using the DEM as input to the Flow Direction tool, the direction in which water would flow out of each cell is determined.
With the Sink tool, any sinks in the original DEM are identified. A sink is usually an incorrect value lower than the values of its surroundings. The depressions shown in the graphic above (the scattered colored points) are problematic because any water that flows into them cannot flow out. To ensure proper drainage mapping, these depressions can be filled using the Fill tool.
Using the Watershed tool, the watersheds are delineated for specified locations. However, if you want to calculate only the stream network, this step can be ignored.
To create a stream network, use the Flow Accumulation tool to calculate the number of upslope cells flowing to a location. The output flow direction raster created in a previous step is used as input.
A threshold can be specified on the raster derived from the Flow Accumulation tool; the initial stage is defining the stream network system. This task can be accomplished with the Con tool or using Map Algebra.
To represent the order of each of the segments in a network, apply the Stream Order tool. The available methods for ordering are the Shreve and Strahler techniques.
Using the Flow Length tool, the length of the flow path, either upslope or downslope, from each cell within a given watershed can be determined. This is useful for calculating the travel time of water through a watershed.