Playa Recharge & Wetness Estimators

Playa Lakes Joint Venture works toward a future where all playas receive voluntary, ongoing stewardship and people benefit from the services playas provide. The Playa Recharge & Wetness Estimators are designed to provide information about some of these benefits, including potential aquifer recharge amounts for future generations and patterns of seasonal wetness.

Frequently Asked Questions

Below you will find answers to frequently asked questions about playas and recharge, how to use the estimators, and the data behind the calculations. Click on a question to expand and see the answer.

We encourage user feedback. Please send us your comments so we can continue improving our playa tools.

QUESTIONS ABOUT PLAYAS

+ Why are playas important?

Playas collect runoff from the surrounding area after rain storms. They are areas of focused recharge, improving the quality of water flowing into the Ogallala Aquifer, and provide important wildlife habitat. Playas work best when they have intact clay basins with no excess sediment or modifications such as pits or ditches and are surrounded by grassy buffers or native prairie that keep sediments, which may carry contaminants, from reaching the playa basin.

To learn more about playas and the benefits they provide, including groundwater recharge, explore the links below:

Playas: An Important Source of Water in the Great Plains
Playas Support Diverse Wildlife
Playas Recharge the Ogallala Aquifer
What the Scientists Say about Recharge through Playas
Playa Modifications

+ How much recharge do playas provide?

Playas are a primary source of recharge for the Ogallala Aquifer, contributing up to 95% of water flowing into the aquifer and improving its quality. Recharge rates beneath individual playas vary considerably — from almost nothing to 10 inches per year — based on a number of factors including depth to aquifer, soil type, amount of soil saturation, evaporation and transpiration, and amount of rainfall. Recharge rates also vary during the playa wet/dry cycle.

According to scientists, an average of three inches per year can be used to estimate recharge through playas across the region. That’s three inches of water the size of the playa moving toward the aquifer each year. While this may not seem like much, the recharge rate through playas is 10 to 1,000 times more than in upland areas. And when you do the math, it adds up to quite a lot. For example, a four-acre playa, which is a very small one, sends approximately an acre-foot of water toward the aquifer. That’s 325,851 gallons of water, more than enough to supply a couple of families for a year. Learn more.

+ How does recharge through playas happen?

According to the USGS report, most recharge occurs through the large cracks that form in the dry, clay soils in the bottom of the playa. During a rainstorm, water runs off the landscape and into the cracks, eventually making its way to the aquifer. Then when soils become saturated and the cracks close, water continues to seep into the soil and slowly moves downward along roots and small channels, as well as along the playa’s perimeter. Recharge during this time happens at a much lower rate.

+ How long does it take for water to reach the aquifer?

Recharge through playas is a continuous process. Water reaching the aquifer today started its journey during our parents and grandparents lifetimes; the water recharging now will be available for today’s children and future generations.

The time it takes for recharge to reach the aquifer and be available for extraction varies depending on depth to the aquifer formation and underlying soil type. If it is shallow, water will recharge in months to years. If the depth is approximately 100 feet, it will take years to decades. If the depth is approximately 200 feet, water will recharge in decades. At the deepest locations, recharge could take a century to reach the aquifer.

+ How do playas improve water quality?

The benefit of a healthy playa — a playa with a grass buffer and no hydrological modifications such as pits or ditches — goes beyond simple recharge. Research shows that water reaching the aquifer through playas is of higher quality than that going through other pathways.

This happens in two ways: first, as rainfall and runoff travel toward the playa, the surrounding grasses trap sediments, which can carry contaminants into the playa; then, as the water moves through the clay floor of the playa, a second ‘cleaning’ process occurs as the soils beneath the playa remove nitrates and other dissolved contaminants. The result is high quality water reaching the aquifer that can then be used by those living on the land.

+ Who benefits from the recharge through a playa?

When a landowner takes actions to increase recharge on his/her property, that water benefits him/her directly. Although water in the aquifer does flow horizontally, flow rates are extremely slow (½-1 mile per 10 years). Thus, the water is functionally compartmentalized in a given area; and in some cases, because of the shape of the aquifer formation, the water accumulates in a location and doesn’t move.

+ How do modifications, like pits and ditches, affect a playa?

A pit may trap and hold water for a longer period of time but at the cost of keeping the rest of the playa functional. If the entire playa basin does not receive water, it cannot go through a critical wet and dry cycle, which is necessary to provide habitat for wildlife and to recharge the aquifer. A pit may also break through or remove part of the clay soil, which will circumvent the cleaning function of the playa.

Once pits are filled, rainwater and runoff can reach the large cracks in a dry playa — which is essential for recharge to occur — rather than collecting in the pit. The shallow water that spreads across the playa also allows plants to flourish, which in turn provides important food and habitat for migrating birds and other wildlife.

QUESTIONS ABOUT THE ESTIMATORS

+ How do I select playas?

To select, click on individual playas (up to 7) or use the circle tool

to highlight multiple playas within an area (the circle tool is only available on the Recharge tab). When using the circle tool, place your cursor in the middle of the area you want to select, then drag it to increase the circle size. Once playas are selected, you can deselect a specific playa by clicking on it again or deselect all playas by clicking the “Clear Selection” button. If you have trouble selecting a playa, you may need to zoom in further.

+ How can I view more information about an individual playa?

To view details about the most recently clicked playa, click on the information icon

. A playa information box will appear and show details about that playa. If you close the box, you can reopen it at any time by clicking on the information icon again.

+ How is the recharge estimate calculated?

The actual amount of groundwater recharge varies, depending on yearly rainfall and the condition of the individual playa. Unless otherwise stated, the calculation uses a rate of 3 inches per year, which is an average recharge rate across our six-state region. Here is an example of the recharge calculation for a four-acre playa:

4 ac x 3 in/yr x 1 ft/12 in = 1 acre-foot of water
1 acre-foot x 325,851 gal/acre-foot = 325,851 gallons of water

+ What do the different colors of playas mean?

In this tool, playas are classified as surrounded by grass (“grassland”), in fields being farmed (“farmed”), or having modifications that change the natural function (“modified”).

Grassland = Included in the recharge estimate.

Farmed = Included in the recharge estimate, but these playas are at risk of losing their recharge capacity if their functionality is not restored.

Modified (e.g., pits, ditches, berms) = Not included in the recharge estimate. There is no scientific evidence to determine recharge amount.

+ How are playa classifications determined?

PLJV periodically assesses playa health with remotely sensed data and information from local partners. For example, the National Agricultural Statistics Service publishes annual estimates of what crops are grown in the US and where. PLJV uses the last few years of this data to understand whether a particular playa may have changed use, from grass to crops or vice versa. Recent changes you see on the ground may not yet be reflected in this kind of data.

Information on whether a playa has a pit or ditch may come from our Playa Modifications Database — a citizen science effort — or recent local knowledge from partner organizations. With over 70,000 playas shifting use and status on a regular basis, classifications will need to be updated over time. If you notice that your playa’s classification on the map does not match what you see, please send us feedback.

+ What does average seasonal playa wetness mean?

The points on the chart represent how often at least part of a playa has been wet during that season over the last 34 years. Playas vary with their context and climate — for example, a value of 12% may represent a playa that holds water for a few weeks every year, or a playa that is typically saturated for months one year in ten. Consider these values in comparison with your own experiences. Another way to use this value is to think of it as the chance that some part of your playa will hold noticeable water during a given season. A zero value indicates very low wetness frequency or insufficient data.

+ How do you know whether a playa is wet or dry?

To find this information, we used imagery from LANDSAT 5 and 8 satellites, dating back to 1985. These satellites orbit the earth every 16 days and collect information about Earth’s surface through spectral analysis (for example, how much light is reflected at a given point, which can indicate whether plants are growing). When confounding features (for example, clouds, snow, and ice) are removed from the images, it is possible to determine the presence of water, as in a playa.

Because the values are remotely sensed from space, some error is expected and values should be understood as approximations. Playas are a particularly difficult problem for remote sensing, as the water is often shallow and interspersed with vegetation, making it harder for the satellite to see. These estimates are therefore conservative, and you may find that your playa is wet even more often.

+ Why isn’t my playa on the map?

The playas you see are a compilation from multiple data sources, as described in our probable playas release notes. Playas were identified from authoritative sources such as federal agencies, or through large-scale research projects taken on at a state level. Each of these data sources has an error rate, and it is certainly possible that playas are missing from these data.

To ensure that all playas have a similar level of rigor in delineation, PLJV does not add playas to the database on a one-off basis. However, we are interested in improving the database over time, and would benefit from any information you have to share. Please send us feedback if you find that a playa is missing.

Funding Partners

Special thanks to USDA Natural Resources Conservation Service and High Plains Underground Water Conservation District for providing funding to develop the Playa Estimators.

RECHARGE
WETNESS

Estimated Recharge Potential
for Future Generations

Playas are a primary source of recharge for the Ogallala Aquifer, contributing up to 95% of water flowing into the aquifer and improving its quality. Click on up to 7 playas, or use the circle tool to select more than 7 in one area, on the map to view the potential amount of recharge they can provide.

To select, click on individual playas (up to 7) or use the circle tool

to highlight multiple playas within an area. When using the circle tool, place your cursor in the middle of the area you want to select, then drag it to increase the circle size.

Once playas are selected, you can deselect a specific playa by clicking on it again or deselect all playas by clicking the “Clear Selection” button. If you have trouble selecting a playa, you may need to zoom in further.

No Information

If “No Information” is displayed, all selected playas are classified as modified

gallons of water per year

The actual amount of groundwater recharge varies, depending on yearly rainfall and the condition of the individual playa. Unless otherwise stated, the calculation uses a rate of 3 inches per year, which is an average recharge rate across our six-state region.

Here is an example of the recharge calculation for a four-acre playa:

4 ac x 3 in/yr x 1 ft/12 in = 1 acre-foot of water

1 acre-foot x 325,851 gal/acre-foot = 325,851 gallons of water

Gallons Acre-feet

Playa Classification

Grassland = Included in the recharge estimate.

Farmed = Included in the recharge estimate, but these playas are at risk of losing their recharge capacity if their functionality is not restored.

Modified (e.g., pits, ditches, berms) = Not included in the recharge estimate. There is no scientific evidence to determine recharge amount.

Average Seasonal Playa Wetness

The points on the chart represent how often at least part of a playa has been wet during that season over the last 34 years. Playas vary with their context and climate—for example, a value of 12% may represent a playa that holds water for a few weeks every year, or a playa that is typically saturated for months one year in ten. Consider these values in comparison with your own experiences.

Another way to use this value is to think of it as the chance that some part of your playa will hold noticeable water during a given season. A zero value indicates very low wetness frequency or insufficient data.

Playas vary widely in when and how often they are wet. These differences can matter when making decisions about how to manage a playa. Click up to 7 playas on the map to compare their patterns of wetness.

To select, click on individual playas (up to 7).

Once playas are selected, you can deselect a specific playa by clicking on it again or deselect all playas by clicking the “Clear Selection” button. If you have trouble selecting a playa, you may need to zoom in further.

Seasons coincide with important dates for agriculture and wildlife.

WINTER: Nov 15 - Mar 14
SPRING: Mar 15 - May 31
SUMMER: Jun 1 - Aug 14
FALL: Aug 15 - Nov 14

Playa ID:

Acres:

State:

County:

Hydrologic modification:

Farmed playa:

Healthy playa:

Historic 35-yr wetness frequency Spring:

Historic 35-yr wetness frequency Summer:

Historic 35-yr wetness frequency Fall:

Historic 35-yr wetness frequency Winter:

HP aquifer saturated thickness 2013 (ft):