GLDAS Runoff 2000 - Present

<div>When precipitation falls on the surface of the Earth, much of it is captured in storage (e.g. lakes, aquifers, soil moisture, snowpack, and vegetation). Precipitation that exceeds the storage capacity of the landscape becomes runoff, which flows into river systems. Overland flow is the most visible form of runoff, causing erosion and flash floods, but subsurface flow is the larger contributor in many watersheds. Subsurface flow can emerge on the surface through springs, or more commonly, seep into rivers and lakes through their banks. </div><div><br /></div><div>In urban areas, impervious land cover drastically increases the amount of surface runoff generated, which sweeps trash and urban debris into waterways and increases the likelihood and severity of flash floods. In agricultural areas, surface or subsurface runoff can carry excess salts and nutrients, especially nitrogen and phosphorus. This map contains a historical record showing the amount of runoff generated each month from March 200 to present. It is reported in millimeters, so multiply by a surface area to calculate the total volume of runoff.</div><div><br /></div><div><font size='3'>Dataset Summary</font></div><div><font size='3'><br /></font></div><div>The GLDAS Runoff layer is a time-enabled image service that shows average monthly runoff from 2000 to the present measured in millimeters. It is calculated by NASA using the Noah land surface model, run at 0.25 degree spatial resolution using satellite and ground-based observational data from the <a href='https://ldas.gsfc.nasa.gov/' target='_blank'>Global Land Data Assimilation System</a> (GLDAS-2.1). The model is run with 3-hourly time steps and aggregated into monthly averages. Review the complete list of model <a href='https://ldas.gsfc.nasa.gov/gldas/GLDASforcing.php' target='_blank'>inputs</a><span>, explore the </span><a href='https://hydro1.gesdisc.eosdis.nasa.gov/data/GLDAS/GLDAS_NOAH025_M.2.1/' target='_blank'>output</a> data (in GRIB format), and see the full Hydrology <a href='https://disc.gsfc.nasa.gov/datasets?keywords=Hydrology' target='_blank'>Catalog</a> for all related data and information!</div><div><br /></div><div><b>Phenomenon Mapped:</b> Runoff</div><div><b>Units:</b> Millimeters</div><div><b>Time Interval:</b> Monthly</div><div><b>Time Extent:</b> 2000/01/01 to present</div><div><b>Cell Size:</b> 28 km</div><div><b>Source Type:</b> Scientific</div><div><b>Pixel Type:</b> Signed Integer</div><div><b>Data Projection:</b> GCS WGS84</div><div><b>Mosaic Projection:</b> Web Mercator Auxiliary Sphere</div><div><b>Extent:</b> Global Land Surface</div><div><b>Source:</b> NASA</div><div><b>Update Cycle:</b> Sporadic</div><div><br /></div><div><font size='3'>What can you do with this layer?</font></div><div><br /></div><div>This layer is suitable for both visualization and analysis. It can be used in ArcGIS Online in web maps and applications and can be used in ArcGIS Desktop. t is useful for scientific modeling, but only at global scales.</div><div><br /></div><div>By applying the &quot;Calculate Anomaly&quot; processing template, it is also possible to view these data in terms of deviation from the mean. Mean runoff for a given month is calculated over the entire period of record - 2000 to present.</div><div><br /></div><div><b>Time:</b> This is a time-enabled layer. By default, it will show the first month from the map's time extent. Or, if time animation is disabled, a time range can be set using the layer's multidimensional settings. If you wish to calculate the average, sum, or min/max over the time extent, change the mosaic operator used to resolve overlapping pixels. In ArcGIS Online, you do this in the &quot;Image Display Order&quot; tab. In ArcGIS Pro, use the &quot;Data&quot; ribbon. In ArcMap, it is in the 'Mosaic' tab of the layer properties window. If you do this, make sure to also select a specific variable. The minimum time extent is one month, and the maximum is 8 years. </div><div><br /></div><div><b>Variables:</b> This layer has three variables: total runoff, surface flow and subsurface flow. By default total is shown, but you can select a different variable using the multidimensional filter, or by applying the relevant raster function. </div><div><br /></div><div><b>Important:</b> You must switch from the cartographic renderer to the analytic renderer in the processing template tab in the layer properties window before using this layer as an input to geoprocessing tools.</div><div><br /></div>