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IRL Report Card: North Indian River Lagoon

The North Indian River Lagoon is a single region that has regulatory targets established by the St. John’s River Water Management District.


The North Indian River Lagoon (NIRL) is connected to the Mosquito Lagoon through the Haulover Canal, which allows water (and algae) to transfer between them. The two bodies of water share the characteristic of having little flushing to the ocean and few river inputs so water stays in place for a long time (i.e. long retention times). This exacerbates temperature and salinity fluctuations and nutrient concentrations that can fuel algal blooms and fish kills.

The North Indian River Lagoon has four tributaries that are scored as part of MRC’s health assessment. They are Turnbull Creek, Big Flounder Creek, Horse Creek, and the Eau Gallie River. Click here to see water quality scores of the tributaries.

Like the Banana River Lagoon, in the North Indian River Lagoon, we see severe fluctuations in water quality driven by the two major algae bloom events in 2010 & 2016. Water quality overall declines somewhat over 25 years and habitat quality declines significantly.

North Indian River Lagoon Water and Habitat Quality



North Indian River Lagoon Tributaries

There are four tributaries that enter the North Indian River Lagoon. Tributary targets were calculated in house based on the TMDL established in each tributary. More information on the tributary targets is included in the Health Assessment Methodology Report.

Water quality scores for the tributaries and the North IRL region show a dramatic differences in water quality between tributaries. Some are historically and continuously poor, others are good and others are improving.

The graph below shows changes in water quality over time in the North IRL and its tributaries. The breaks in the lines and the empty cells in the table below are years that no data were collected in that tributary. It is interesting that water quality in the lagoon proper and the area tributaries go up and down together. This could indicate that it is poor water quality in the tributaries that is influencing the lagoon’s water quality or that whatever is driving water quality in the lagoon is also driving water quality in the tributaries. It is also interesting that the northernmost tributaries (Turnbull Creek and Big Flounder Creek) mimicked water quality of the IRL North in 2016, but the tributaries located more south in that region (Horse Creek and the Eau Gallie River) did not.

North Indian River Lagoon & Tributaries Water Quality