MyPond capability
Watershed delineation and runoff analysis
Find out what drains into your pond, and what it carries.
MyPond delineates the land area that drains into a pond and then characterizes it. Starting from the pond as the pour point, it traces flow downhill across USGS 3DEP LiDAR elevation to find the contributing drainage area, then reports how large that area is, how it compares to the pond, what land cover is in it, what its runoff curve number is, and how many mapped stream miles enter it. This is the layer that explains why a pond keeps getting nutrients no matter what is applied to the water itself.
Inputs, analysis, outputs
What you provide
- The pond footprint
- The traced shoreline is the pour point. No survey, no upload, and no knowledge of your property boundary is required.
What MyPond does
- Flow delineation over LiDAR elevation
- MyPond samples ground elevation around and above the pond and traces the flow path downhill to determine which land actually contributes runoff to this pond. A LiDAR surface at 1 to 3 meters resolves the small berms, road grades and ditches that decide where water goes on flat ground, which coarser elevation data smooths away.
- Land cover tally
- The delineated area is intersected with federal land cover mapping and reported as acres and percent for each class: row crop, pasture and grassland, forest, wetland, open water, developed and impervious.
- Runoff curve number
- A curve number is derived for the watershed from its land cover and its soils. It is the standard measure of how much of a given rainfall leaves as surface runoff instead of soaking in: a low number is a forest on sand, a high number is a parking lot or a saturated clay pasture.
- Stream inflow count
- Mapped stream segments entering the watershed are counted and their total length measured, which distinguishes a pond fed by a real channel from one fed by sheet flow or groundwater.
What you get back
- Watershed area
- In acres.
- Watershed to pond ratio
- Drainage acres per surface acre of pond. It is the single most diagnostic number on the page: a high ratio means the pond is a catchment and its water chemistry is mostly decided upstream.
- Land cover breakdown
- Percent crop, pasture, forest, wetland, developed, impervious.
- Runoff curve number
- And percent impervious surface.
- Mapped stream count and stream miles
- Entering the delineated area.
- Watershed soils and bedrock
- The same soil and geology analysis, run over the whole drainage area rather than the pond footprint.
How it works
Why the watershed decides the pond
Nutrients, sediment and alkalinity mostly arrive from the drainage area, not from the pond itself. A pond with a 40 to 1 watershed ratio below row crop is receiving a nutrient load that no in-pond treatment will out-run, and knowing that changes the recommendation from repeated algaecide to inflow management. A pond with a 2 to 1 ratio fed by forest has almost no external load, which points an algae problem at internal cycling from the sediment instead.
Why elevation resolution matters here
Watershed boundaries on gentle terrain are decided by features a meter high. A 10 to 30 meter elevation surface will often route a field into the wrong basin entirely. LiDAR at 1 to 3 meters keeps the field with the pond it actually drains to.
What delineation cannot see
Tile drainage, culverts and pumped inflows move water in ways surface elevation does not show. A delineated watershed is the gravity-fed contributing area, and a tile line from a neighboring field is a real input it will miss. The land cover tally is also a snapshot of the mapped land cover, so a field that changed use recently reads as its mapped class until the source updates.
Where the data comes from
- USGS 3DEP
- The USGS 3D Elevation Program, a national elevation dataset built largely from airborne LiDAR at 1 to 3 meter resolution across the lower 48. MyPond samples it around and above the pond to get real ground surface shape instead of an assumed slope.
- National Land Cover Database
- The federal land cover raster. Once the drainage area is delineated, MyPond tallies what is actually in it: row crop, pasture, forest, wetland, developed and impervious surface, each as acres and as a percentage of the watershed.
- National Hydrography Dataset
- The federal mapping of streams and flow lines. MyPond counts the mapped stream segments entering the delineated watershed and their total length, which separates a pond fed by surface flow from one fed mostly by groundwater or direct rainfall.
Common questions
What watershed to pond ratio is healthy?
It depends on land cover more than on the ratio alone. A large watershed of forest can be easier on a pond than a small one of row crop. MyPond reports the ratio next to the land cover breakdown because the two only mean something together.
Do I need to know my property lines to get a watershed?
No. The drainage area is determined by terrain, not ownership, and it frequently extends well past a property boundary.
Does the watershed analysis include the soils upstream?
Yes. The soil and bedrock analysis is run over the delineated watershed as well as the pond footprint, so runoff chemistry and infiltration are characterized for the contributing area.
Related
MyPond is built by Natural Waterscapes. See live data from a real pond, or what it costs.