Photo Courtesy of the Edwards Aquifer Authority
Written by Christopher Ray, Professor of Earth Sciences at San Antonio College and Cory Foshée, AAMN
Hydrology is the study of water near or at the land’s surface that generally focuses on freshwater processes but can also include the study of saltwater lakes (i.e. the Great Salt Lake). Hydrology has a couple of different disciplines such as Surface Water Hydrologists, who focus on catchment systems, rivers, streams, and lakes; and Groundwater Hydrologists – who focus on the water that has seeped underground into the soils, sediments, and rocks beneath the surface. However, in general, both types of systems are interconnected and go hand in hand. There are also hydrologists that specialize in water quality, geochemistry, and even geomorphology – which is the study of how rivers and streams shape Earth’s surface overtime. Overall, hydrologists study the freshwater processes that we’ve all come to rely on.
THE IMPORTANCE OF HYDROLOGY
Aside from life’s reliance on water, sometimes water can potentially be a hazard. Groundwater is pumped out for use because it tends to be cleaner, requires less filtration, and less treatment. Living along river systems, we can source our water from rivers but generally, we prefer to use groundwater. With living near river systems, one also needs to be aware of flood hazards. Hydrologists are able to look at the discharge in rivers and historical flood records. From this information, they can advise on the type of infrastructure that can be built nearby, as well as zoning areas for parks.
Groundwater here in San Antonio is a big issue because we source most of our water from the Edwards Aquifer. Being able to study how the aquifer is recharged and how the water flows within it, and our effects of pumping the water out, are all areas of focus for hydrologists.
THE WATER CYCLE
The water cycle is our conceptual model for the flow and movement of water through the different reservoirs of the hydrologic cycle. The biggest reservoir is the ocean. The ocean is the source of most of the water vapor that condenses and falls as precipitation on the land. Once water is on land, this is where it gets exciting because a couple of different things can happen. One, you can get runoff – water that flows to the rivers and streams, or two, you could have infiltration – this is the water that seeps into the soils and eventually flows as groundwater. And then you have biological processes such as when plants pull that moisture from the soil, transpire it, and release it back into the atmosphere, eventually trying to make its way back to the ocean, and it just keeps spinning!
POTENTIAL CHALLENGES BROUGHT ON BY CLIMATE CHANGE
In our region we are along what is called the 100th Meridian – the imaginary border between the humid East and the dry West. We get about half the amount of rain that Houston receives, but double the rainfall of El Paso. Our climate is what’s considered to be semi-arid.
One of the ideas regarding climate change is that it will lead to a redistribution of storm patterns and rainfall patterns. The 100th Meridian will then start to ease its way East – this means the eastern portion of the U.S is predicted to get wetter and the western portion is predicted to get drier. Since our region is right on the cusp of the two, we may start to see drier conditions and prolonged periods of drought. With this in mind, we have to consider how we are going to sustain the water resources we rely on.
Other studies have shown that storm intensity may increase whereas the average number of storms may remain the same, but the storms we do experience will be stronger. As the oceans warm, evaporation increases fueling larger and larger storm systems.
THE SAN ANTONIO RIVER AND THE EDWARDS AQUIFER FOR HYDROLOGICAL STUDIES
The Edwards Aquifer is heavily studied and much research on it is carried out by the Edwards Aquifer Authority, as well as at UTSA’s Institute for Water Research. The Edwards Aquifer is the source of water feeding springs that are the headwaters for many of the rivers in the region.
WHICH NATIVE PLANTS AND ANIMALS RELY ON THESE BODIES OF WATER?
There are many animals that rely on the San Antonio River, nearby creeks, and neighboring riparian areas. These include but are not limited to: Largemouth Bass, Yellow Bullhead, Red-eared Sliders, the Comal Blind Salamander, Raccoons, White-tail Deer, Cottontail Rabbits, Whooping Cranes, and Ospreys (sanantonio.gov).
Some of the many plants that can be found in or near our waterways include Taxodium distichum (Bald Cypress), Platanus occidentalis (American sycamore), Ceratophyllum demersum (Hornwort), Epipactis gigantea (Chatterbox), Potamogeton nodosus (Longleaf Pondweed), and Cephalanthus occidentalis (Common Buttonbush).
HOW CAN MASTER NATURALISTS/CITIZENS HELP WITH HYDROLOGY?
One of the best ways to help maintain a good water supply is to be mindful of water restrictions that are in place. Only water your lawn at certain parts of the day and if there are water restrictions for only certain times of the week, you should really follow these! Realize that you do not have to water every day, especially if you plant native grasses such as Buffalograss (Bouteloua dactyloides) or Blue Grama (Bouteloua gracilis). Another way you can help is by always making sure to dispose of harmful materials properly – such as motor oil, paints, flea collars, household cleaners, and medicines (epa.gov).
References
Epa.gov (2024) Household Hazardous Waste (HHW) https://www.epa.gov/hw/household-hazardous-waste-hhw
Sanantonio.gov (2014) Water Facts & Impacts https://www.sanantonio.gov/Remember-the-River/Get-the-Facts/Water-Facts-and-Impacts#:~:text=River%20Authority%20webpage.-,San%20Antonio%20River,Sunfish%2C%20Channel%20Catfish%2C%20Red%20Shiner