What Are Hydrologist Tools?

Flow Accumulation

• Flow accumulation involves measuring how water flows downstream based on the accumulated weight of the water. The tool uses the cell weight that flows downstream via an output raster. A raster is an image that uses a square or rectangular grid with different color points or pixels. In this case, each box of the grid uses an arrow to point in what direction the water flowed. The flow accumulation tool uses this data to calculate and output the flow based on the direction of the flow and how the cells flow into one another. If a cell weight is not provided, the tool gives that cell a value of one. To use this tool, you must input the express, the true raster or constant and the conditional raster.

Staff Gage

• A staff gage is a tool that hydrologists use to determine the height of a waterway, including flumes, streams, rivers, reservoirs and irrigation channels. Generally, these gages are usually made of iron, but older gages are often wood. Five main styles of gages are used: A, C, E, M, T and W. The A gage is 4 inches wide and comes in 3 1/3 sections, which you can combine to reach nearly 100 feet. The gage shows both the foot and tenth of a foot measurements. The C gage shows hundredths of a foot, and it is broken up by tenth of a foot and foot sections. It is 2 ½ inches wide. The E gage is 3 1/2 inches wide, and it comes in 1-, 2- or 5-foot sections. It shows data and tenths of a foot and foot measurements. The M gage uses the metric system and is broken up by decimeters and centimeters. It is 3 1/3 feet long and 2 1/2 inches wide. The T gage also uses the metric system and is 3 1/3 feet long and nearly 6 inches wide. It has black numbering on a white background. Two minor styles are the Style O, which uses black numbers on a yellow back or red lettering a yellow background, and Style W, which is used on 3-inch pipes.

Fill

• The Fill tool combines different tools into one: flow direction, focal flow, zonal fill and watershed. It helps you find sinks, which are errors associated with data resolution and where data is too low. Once you find the sinks, this tool will fill them within a specific Z limit. Filled sinks are a different color from the main graph. You can also use this tool to deal with peaks, which are another type of error where the data is too high. To use this tool, you must know Z limit and input/output surface raster.