resources in the Tierra Blanca generally, we sought to investigate our playas specifically through lenses of water quality and quantity. Image: Boehning playa ...
Water quality, quantity, and usefulness of playa systems in the Texas High Plains Nathan Howell1, Erick Butler1, Bridget Guerrero2 1School
of engineering, computer science, & math, West Texas A&M University; 2Dept of agricultural sciences, West Texas A&M University
ABSTRACT
STUDY LOCATIONS
What are playas?
Playas are the most dominant and noticeable surface water feature in the Texas Panhandle. They may be defined as, “shallow, depressional recharge wetlands occurring in the Great Plains region that are formed through a combination of wind, wave, and dissolution processes with each wetland existing in its own watershed” (Smith 2003). We monitored water quality and quantity parameters of playas in the summer of 2016 via weekly environmental sampling. All playas were in the west Texas Panhandle County of Deaf Smith, an area of mixed use agriculture including concentrated animal feeding operations, croplands, small-to-medium urban centers, and a few agricultural product processing facilities. The purpose the study was to provide some local and timely reference data on water quality and quantity, which would be informative towards the usefulness of playas. Thus far, data reveals that water quality does vary substantially from playa to playa depending on local soils, drainage area, and land use within the watershed. Discussions within landowners and the data itself generally indicate that playas, containing water of sufficient quality and quantity for use only infrequently and unpredictably, do not hold much promise for traditional agricultural or municipal needs. Playas are, however, useful as a means of monitoring processes which are occurring in semi-arid watersheds and likely will hold economic value for ecosystem services and areas of more intense biodiversity. Their ability to hold sway in the minds of a landowner and a local community will likely lie in our ability to demonstrate the value of ecosystem services and biodiversity especially through monetization. Moreover, in the interest of sustainability, in all meanings of the term, it is hard to conceive of a water management strategy in the playa regions which does not appropriately take them into account.
Playas (figure below) may be generally defined as, “shallow, depressional recharge wetlands occurring in the Great Plains region that are formed through a combination of wind, wave, and dissolution processes with each wetland existing in its own watershed (Smith, 2003).” This definition distinguishes them from other types of surface waters which are sometimes conflated in the term “playa” including prairie potholes, ephemeral lakes, or other wetland features. The Great Plains playas thus are somewhat unique in formation and ecologic function. Most are on private land, and the way in which they are managed sometimes indicates what the value of the playa is to a property owner. These various uses include direct farming, livestock watering, stormwater, wastewater storage, and occasionally even irrigation. There is not a consensus on what the most sustainable and viable use for them is or should be. Within the context of investigations on water resources in the Tierra Blanca generally, we sought to investigate our playas specifically through lenses of water quality and quantity.
Each study location was unique and had its own drainage area. All three playas contained water when monitoring began on July 5, 2016. By the time detailed water monitoring ceased at the end of July all had lost some water. Stocker had virtually none remaining.
Land use analysis To identify land use near the playa, an analysis was made using the 2006 National Land Cover Dataset (NLCD 2006). Land use classifications were made at the playa site and within the 12-digit Hydrological Unit Class (HUC-12). Results are presented below. a
b
c 1%
1%
5% 6%
28% 66%
11 21 22 23 24 31 41 42 52 71 82 90 95
3% 2%
16%
11
4%
11
21
21
22
22 23
31 42%
41
31 41 76%
50%
43 52 71 82
43 52 71 82 95
95
Land use cover of the 12-digit hydrological unit class (HUC-12) for each playa using the 2006 National Land Cover Dataset Classifications (NLCD 2011)—a)Betzen, b)Boehning, and c)Stocker.
credit: Playa outlines were determined by L. Barbato and K. Mulligan at Texas Tech Center for Geospatial Technology.
RESULTS
Water quality of playas Four weekly monitoring events for in situ measurable water quality parameters in summer 2016. Some significant rains and certainly significant evaporation caused variation in all playas but not necessarily in correlated ways. An constructed pond and also a stream were monitored for context. (not pictured here)
Image: Boehning playa 2016-07-13
OBJECTIVES Description of National Land Cover Dataset Classifications.
1)Characterize water quality of Tierra Blanca playas during summer wet season. 2)Relate water quality and quantity of playas to land use and hydrological rainfall-runoff. 3)Use physical-chemical data from playas to make recommendations on playa economic value and usefulness.
BACKGROUND
Using the 2006 National Land Cover Dataset Classifications, the land cover of the HUC-12 that contains each playa is primarily grassland/herbaceous and cultivated crops (Class 71 and 82). There seems to be a small amount of open space for development within the area.
Where is the Tierra Blanca Watershed? The Tierra Blanca watershed (figure below) comprises a portion of the western half of the Texas Panhandle and a bit of eastern New Mexico. With a drainage area of 4960 km2 (1920 mi2), the watershed is comprised of a relatively low population (7.2 pop/km2) and is largely agricultural. The majority of supplied water comes through groundwater pumping of the Ogallala and Dockum Aquifers. And yet the story of water within the Tierra Blanca watershed is not defined entirely by rain, runoff, drainage lines, and creeks. There is also the most predominant surface water in this region, the playa.
STUDY DESIGN The best way to understand the water quality of playas/ephemeral wetlands of this type is to actually sample them at a regular interval when they contain water. In the summer of 2016, the approach we took to both determine playas that would be representative of the region and begin characterizing there waters is shown below.
Identify locations Determine location of all playas in watershed Screen locations according to playa size and likely drainage area Make site visits to most promising locations Consult with local land owners and NRCS to identify most likely private property access Examine accessible playas according to which ones most likely to have water
Location Map
FINDINGS THUS FAR
Weekly site visits Make physical observations at each location Take photos from several directions to track water surface elevations Retriever water depth logger information Record in situ water quality information Take composite grab samples from playa waters
Interpret data in context Retrieve weather data from West Texas Mesonet Analyze grab samples for major and minor ions, TSS, and TOC Build model of playa bottom elevation to examine water volume storage in time
Water quantity of playas Water depths were measured at 10 second intervals as pressures. Correction made using local weather station barometric .pressure.
• Data analysis continues with estimates of playa water volumes estimates in time using survey elevations. • Runoff did enter at least one playa during monitoring. Its effects still being determined. • Dissolved oxygen in all three playas usually high enough to support aquatic life. • TDS often lower than nearby groundwater wells. Thus, at least one parameter better than ground water currently used on these properties.
References Fry, J., Xian, G., Jin, S., Dewitz, J., Homer, C., Yang, L., Barnes, C., Herold, N., and Wickham, J., 2011. Completion of the 2006 National Land Cover Database for the Conterminous United States, PE&RS, Vo77(9):858-864. Mulligan, K. R.; Barbato, L. S., Playas and Wetlands Geodatabase. In March 2014 ed.; USDA-ARS, Ogallala Aquifer Program: 2014. National Geographic 2011, National Geographic, Esri, DeLorme, NAVTEQ, UNEPWCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, iPC, (2011). National Geographic World Map, digital topographic basemap of the world. Accessed online http://www.arcgis.com/home/item.html?id=b9b1b422198944fbbd5250b3241691b6 on 07.06.2017 Smith, L. M., Playas of the Great Plains. 1st ed.; University of Texas Press: Austin, 2003 of
Acknowledgments
This project is being funded by the USDA National Institute of Food and Agriculture (NIFA) under award no. 2015-68007-23189.
