I.Water levels in the Ciénega

Two methods are being used to determine water levels inside the Ciénega. One is through manual reading of water level at stream gauges, and one by using pressure-based water level loggers.

Water gauges

We are using WaterMark® Stream Gauges to manually record water elevation in the Ciénega. These water gauges have a special porcelain enamel finish to ensure easy reading and resist rust or discoloration and are graduated in metric units.

A total of 20 water gauges have been installed throughout the Ciénega. The following map shows the location of these gauges. These gauges are measured on a biweekly basis or at least once a month.

An example of a WaterMark® water gauge – site #13

Each water gauge has been referenced to mean sea level so that maps of water surface and depth can be created. The map below shows an example of the water surface elevation for the month of March 2010.

Pressure-based water level loggers

The network of pressure-based loggers consists of 13 sites; originally 14 but we lost one due to vandalism. Two types of loggers are being used, eight are YSI and six are HOBO loggers. Seven sites have a YSI logger and five sites have a HOBO logger.

The YSI loggers include six 600 LS and two 600 XLM, both of which used a vented level system to measure water level; that is they consider barometric pressure. All YSI loggers measure salinity, specific conductance and total dissolved solids (TDS). In addition these parameters, the 600 XLM measures dissolved oxygen and pH/ORP. On the other hand, the HOBO loggers measure water level with a non-vented system and temperature. We are using the HOBO loggers because they are not as expensive as the YSI and can be used in samplings sites that are more susceptible to vandalism. All loggers are measuring water level every hour, and data is being downloaded every month.

An example of a site with a YSI sensor. The sensor is installed inside a 4” PVC pipe that is attached to a frame. The YSY sensors have a vented system that requires a cable from the sensor to be outside the PVC to measure and account for barometric pressure. Each PVC pipe has a plug with a lock to prevent vandalism.