Although we can reasonably monitor precipitation, stream flow, reservoir capacity, and groundwater levels, soil moisture is more difficult to quantify. As drought continues in Texas, water managers are becoming more aware of the link between the soil moisture deficit and water resources. For example, the 2011 drought in Texas resulted in total water storage deficit of over 62 km3 with soil water storage accounting for 20-100% [Long et al., 2013]. This high uncertainty is related to the output from numerous land surface models which cannot be constrained further until real soil moisture data is available. However, soil moisture monitoring is sparse in Texas. Researchers at The University of Texas at Austin -in collaboration with NASA, are designing TxSON to provide:
- Refined soil moisture satellite products for operational use and improved forecasting.
- Improved drought management monitoring and irrigation water requirements.
- Data for utilities and industry to meet water, wind, and energy demands.
- Real-time emergency response data for natural disasters and environmental emergencies.
|In comparison to other states, soil moisture and meteorological networks are sparse in Texas. The Texas Soil Observation Network (TxSON) near Fredericksburg will serve as the state’s first intensively monitored region (inset) for calibration and validation of satellite and land surface model products.
Where is the water in Texas?
Though droughts and floods are inevitable in Texas, the impacts are inherently linked to antecedent soil moisture conditions. When saturated, soils are prone to flood. When dry, soil water must be replenished before excess water can replenish streams and aquifers. A lack of consistent rainfall affects crop and rangeland production resulting in meteorological drought. Prolonged dry conditions result in hydrological drought impacting deeper soil water storage that must be replenished before water can enter reservoirs or recharge aquifers. A time lag exists between these types of droughts, leaving the public wondering why a drought persists even after normal rainfall returns.
During the 2011 drought in Texas, UT researchers estimate a total water deficit of 50 million acre-feet (MAF) with soil moisture accounting for 20-100 percent of this shortage. This amounts to a lot of water considering Texans currently consumes 18 MAF annually. This equates to 3.5 inches of rain over the entire State (if rain could fall evenly across TX!). Without on-ground data, we can’t predict where these losses have occurred, nor can we estimate the amount of precipitation needed to overcome a drought or conversely, produce flooding. The 2011 drought shows us that neither satellites nor numerical models alone can accurately determine “where” the water is without ground-truth points.
This project’s goal is to build a reliable measurement system that connects soil water to surface water and groundwater resources, providing water managers and stakeholders with a more comprehensive ability to assess Texas’ water demand.
|Total terrestrial water storage measured by NASA’s GRACE satellite over Texas shows changes in the Earth’s gravity resulting from gains (blue) and losses (red) of water weight. Change in soil moisture estimated from land surface models is illustrated by the green line and reservoir storage by the dark blue line. The variability of state-wide soil water storage is considerably more than the changes we see in our reservoirs.
Texas Soil Observational Network (TxSON)
The TxSON is an intensively monitored area (500 square miles) located near Fredericksburg, Texas, along the Pedernales River and within the middle reaches of the Colorado River. TxSON consists of 36 new monitoring stations along with 7 existing stations of the LCRA Hydromet network in support of NASA’s Soil Moisture Active Passive (SMAP) program, which will produce global coverages of soil moisture and significantly enhance our weather forecasting skills. Locally, TxSON will help residents, and local and State agencies of Texas recognize the linkages between soil moisture, crop/rangeland production and water resources while generating high quality data for the NASA mission. This unique network will produce:
What can you do?
A focal point for hydrologic monitoring in a vital area for Texas water resources
An important first step in building a monitoring network across Texas, one of the most under-monitored areas in the country
Collaboration and outreach to enrich educational resources and promote conservation
We need funding and access to land to expand the network beyond eastern Gillespie County. Donate a station through the Jackson School of Geosciences.
TxSON participating partners:
A single station requires a 10 x 10 foot fenced are and periodic assess to collect soil samples and do routine maintenance.
To install a station, we auger a small hole (12 inches wide, 36 inches deep), install soil moisture sensors into the side walls, and backfill the hole. Meteorological sensors, a data logger and a cellular modem are added to a tripod on the surface. The system is self-contained and powered by a solar panel. Data (soil moisture and temperature, rainfall, air temperature and humidity) are automatically transmitted to an external server and are available in near real-time at LinkToDataPage.
Expansion will depend on donations or state support. Ultimately, we envision TxSON serving the entire State of Texas.