Overview
Water level measures the changes in depth of a body of water over a period of time. Daily fluctuations in water level are a common characteristic of many water bodies, including saltwater and freshwater estuaries.
Influencing Factors
Water level undergoes daily, seasonal, and annual changes. It is mainly affected by tides or seiches (tides affect salt water and seiches affect fresh water). The amount of precipitation also affects water level. Storms cause short-term increases in water level, whereas the amount of precipitation over the course of several years can have long-term impacts.
In saltwater estuaries, tides have a dramatic influence on water level. High tides push saltwater far up into the estuary, whereas low tides allow freshwater to drain farther out towards the ocean.
Water level in freshwater estuaries does not fluctuate as much as in saltwater estuaries. The water level in an adjoining lake will influence how quickly water drains from a freshwater estuary, or if lake water is pushed up into the estuary.
Importance
Water level affects the biology and chemistry of estuaries. Animals and plants that live in estuaries must be adapted to water levels that constantly rise and fall. Water levels in the rivers, oceans, and lakes adjacent to the estuary will affect how much fresh water and salt water enters and leaves the estuary.
The amount of freshwater and saltwater that enter and leave the estuary will affect water circulation patterns and water chemistry parameters, such as salinity, dissolved oxygen, and turbidity. Long term monitoring will help determine how water level relates to precipitation and climate change, and the long-term effects of changing water levels on estuarine ecology.
Measurement
Water level is typically reported in feet or meters of water depth. Pressure transducers are commonly used to measure water level. Water pressure is measured using the transducer and converted to a depth measurement by using the proportional electrical signal. The sensor can account for factors that change the density and pressure of water, such as temperature and salinity.