In this tutorial, we will learn the QGIS workflow to calculate Areal Mean Rainfall using the Thiessen Polygon method. These methods are suited when the distribution of the rain gauge station is uniform and dense. Using multivariate regression or Kriging techniques, one can account for spatial autocorrelation and can achieve better accuracy. Geostatistical Methods: Rainfall is strongly influenced by local factors - such as elevation. Once the grid points have all been estimated they are summed and the sum is divided by the number of grid cells to obtain the areal mean precipitation. This method is suitable when the rain-gauge network is dense.ĭistance Weighting/Gridded - This is an interpolation technique where a raster grid is created and a value for each pixel is estimated based on the distance to stations. It assumes that rainfall between 2 isohyets is homogeneous.
Iso-hyetal Method: This interpolation technique calculates Isohyets - lines joining equal precipitation. These assumptions are fine for low-lying or flat terrain, but not suitable for mountainous terrain. This method is also called an area-weighted average. Thiessen Polygon: This method divides the area using Thiessen polygons with the assumption that rainfall is homogeneous within the coverage area of each station. This method assumes that the rainfall field is homogeneous and that the rain gauge observations are independent and give equal weight to all rain gauges. By using the rain gauge location and observed precipitation, one can estimate the average precipitation at a given location by using any of the following techniques:Īrithmetic Average: One can simply take an average of all the observed values. often need the average depth of rainfall in a hydrological basin as an input - which is also called Areal Precipitation or Areal Mean Rainfall (AMR).ĪMR calculation can be done using rain gauge data. Batch Processing using Processing Framework (QGIS2)Ĭalculating Areal Mean Rainfall (QGIS3) ¶Ĭalculation of water balance, flood modeling, runoff forecasting, climate studies etc.Searching and Downloading OpenStreetMap Data.Running and Scheduling QGIS Processing Jobs.Writing Python Scripts for Processing Framework (QGIS3).Using Custom Python Expression Functions (QGIS3).Running Processing Algorithms via Python (QGIS3).Getting Started With Python Programming (QGIS3).Calculating Areal Mean Rainfall (QGIS3).Travel Time Analysis with Uber Movement (QGIS3).Service Area Analysis using Openrouteservice (QGIS3).Locating Nearest Facility with Origin-Destination Matrix (QGIS3).Basic Network Visualization and Routing (QGIS3).
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