Utilizing online resources for hydrological research [Part 1]

Introductory words:

Many of us familiar that online resources available for water resources/hydrological research but the same way many of us don’t really know where and how to get those data easily in a usable format. Various problems we face when we desperately need some data, among them finding the exact site and getting the exact data is most notable. Often it happens  that we become ambiguous to see too many information given in the web site and we could not find the required one that we need. Here in this post we will see how to get some environmental data needed to build a hydrological model and process them in a usable format. There are varieties of data available but we will focus only the listed below. Once again these data`s are completely FREE OF CHARGE!!

[1] Administrative Area Map (Shape file)

[2] Digital Elevation Model (DEM)

[3] River Network

[4] Land use Map

[5] Digital Soil Map

[1] Administrative Area Map

Administrative area maps are very useful to when we want to have basic information for some specific region. It is often difficult to find administrative area of developing countries or some specific island therefore a group of researcher made it possible geo referencing all the region of the entire earth and putting them all together in the GADM website [1A]. The file formats are ESRI shape file [1B], or (.kmz) files for Google earth plugin.

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Citations:

[1A] Global Administrative Area website

[1B] About shape file [ESRI website]

[1C] Use of shape files [Based on wiki]

[2] Digital Elevation Model

Digital elevation model (DEM) represents the elevation of Earth’s surface, including features (vegetation, buildings, etc.).A DEM can be represented as a raster a grid of squares, also known as a height map when representing elevation [2A]. They are very useful for watershed/hydrological modeling [2B]. Especially they play significant role for flood mapping and modeling spatial extent of food [2C]. Traditionally elevation was derived by direct survey of the land, and then photogrammetry techniques allowed for terrain extraction with a pair of images with stereoscopic techniques. Today, highly accurate digital elevation can be achieved with light detection and ranging (LIDAR) and interferometry synthetic aperture radar (IfSAR). The SRTM digital elevation data, produced by NASA originally, is a major breakthrough in digital mapping of the world, and provides a major advance in the accessibility of high quality elevation data for large portions of the tropics and other areas of the developing world [2D]. Beside academia DEMs are commercially used for geographic analysis especially urban and regional planning [2E]. Globally available DEMS has approximately 1 km resolution from GTOPO30 and 90 m accuracy from the Shuttle Radar Topography Mission (SRTM) [1].

There are various ways we can download DEM from SRTM site but I found the easiest way of quick download using Google earth plugin [2F]. Here is the video clip to have quick access of SRTM DEM and processing steps to make better use of it.

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Citations:

[2A] Digital Elevation model basicintroduction [wiki]

[2B] Application of Digital ElevationModel for hydrological analysis [ESRI web]

[2C] The use of digitalelevation models for flood hazard mapping:

[2D] SRTM 90m Digital Elevation Databasev4.1

[2E] Applying GIS for populationdistribution under traffic impacts

[2F] CGIAR website with SRTM data

[3] River Geometry Map:

Steam geometry maps are extremely important for flood modeling and management. [3A]. River network is useful for basin delineation [3B]. HydroSHEDS is a mapping product that provides hydrographic information for regional and global-scale applications in a consistent format [3C] It offers a suite of geo-referenced data sets (vector and raster) at various scales, including river networks, watershed boundaries, drainage directions, and flow accumulations. HydroSHEDS is based on high-resolution elevation data obtained during a Space Shuttle flight for NASA's Shuttle Radar Topography Mission (SRTM). The goal of developing HydroSHEDS was to generate key data layers to support regional and global watershed analyses, hydrological modeling, and freshwater conservation planning at a quality, resolution and extent that had previously been unachievable. Available resolutions range from 3 arc-second (approx. 90 meters at the equator) to 5 minute (approx. 10 km at the equator) with seamless near-global extent.

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Citations

[3A] River flow forecasting usingartificial neural network

[3B] watershed delineation process[ArcGIS website]

[3C] HydroSHED web site

[4] Land cover map:

Land use maps often called zoning maps are basically derived from the satellite images and classifying them [4A]. Wide application of land use maps mostly for demographic features and Eco hydrological research[4B ]. They are often used for impact assessment of climate change due to vegetation change and demographic features [4C]. Environmental impacts and land at risk from land degradation such as salinity, flood, drought, and erosion studies can be done with land use maps. Land use maps are prepared by several government agencies, for a variety of reasons. Individual groups and organizations can also generate maps with land use information. Often, such maps are publicly available, so that people who are interested in land use trends can access them. For global application European Space Agency (ESA) provides maps in different time slice. They 

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citations

[4A] About land use map [wiki]

[4B] Land cover maps for ecologicalresearch

[4C] The Importance of Land-CoverChange in Simulating Future Climates

[5] Digital Soil Map

Digital soil map provides type of soil and their physical properties. Soil properties have immense importance for agricultural productivity and application of fertilizer. Soil map can be prepared by survey or classifying the remote sensing images [5A] robust application of soil maps is most often related to irrigation requirement and scheduling. Food and Agricultural Organization of united nation provides soil map with 1:10000 scale classifying 6998 soil classes for entire world. This can be obtained from the geo network web portal of FAO [5B]. Organic and inorganic components are including with the attribute table provided by FAO which is very useful for agricultural research [5C].

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Citations:

[5A] Soilsurvey and mapping using remote sensing

[5B] Geo network web portal for FAOsoil map

[5C] Description of organic and inorganic comment of soil properties from FAO.

Concluding remarks [For part: 1] 

Few issues needed to be discussed, among them projection system and resolution of data needs attention. In most cases the standard projection system is GCS WGS 1984 where the distances are calculated on Arc second. Usually 1 degree equals to 100 km. Since I used ArcGIS they have a default projection of GCS WGS 1984. There might be some error messages or dis placement of maps if the projection system is not similar with the data frame and the extracted data from different sources!!

Here it ends the part 1 of extraction of freely available online geographic data for Environmental/Hydrological/Geographical research, the next section I will be focusing CLIMATIC data [Precipitation, Temperature, Wind speed Solar radiation etc etc.] freely available. So keep tuned....