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Why do we measure subsidence?
In the simplest terms, it keeps us from “flying blind”. Groundwater can be a significant freshwater source, but it is increasingly important that we use it wisely. The harmful effects of pumping too much groundwater must be minimized, and measuring subsidence plays a key role in this. The more data we have, and the more accurate that data is, the easier it is for us to maintain a necessary balance.
Measurements not only provide us with data on changes in land elevation, but they also provide us with the data necessary to calibrate models. Why is this important? It allows us to “see” into the future. Through these sophisticated groundwater and subsidence models, we can predict the results of future groundwater pumpage. This means we can plan ahead…developing groundwater regulations that will prevent foreseeable subsidence.
How do we measure subsidence?
The need for data and the distribution of that data is key. As early as 1906, surveys were conducted throughout the Houston area to establish permanent benchmarks (some of which are still used today). Over the years, subsidence measurement methods have evolved from manual site measurement of benchmarks to satellite-based technology, and for the Subsidence Districts, the goal has always been the same: to monitor the effects of groundwater withdrawal within our area(s), and to take appropriate actions based on those measurements.
All land measurement systems have been developed and controlled by the National Geodetic Survey (part of the National Oceanic and Atmospheric Administration – NOAA). From the creation of the HGSD and FBSD to present-day, the NGS has been an integral partner…serving as counselor, setting standards, studying and housing data, and much more.
For a more detailed look at the different measurement methods used over time, and for a peek at where we may be headed in the future, click on the provided links in this section:
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