The water quality segment report is designed to describe prevailing water quality in a segment and to provide a basis for decision making in the continuing effort to maintain and improve the quality of Texas' surface waters. Periodic updating of the report offers a basis for evaluating the success of past and present programs concerning the segment. The Laguna Madre, Segment 2491, is the elongate bay lying between the lower third of Texas' Gulf coast and Padra Island. It is part of an estuary, a partially enclosed body of water that has a free connection with the open sea and within which sea water mixes with fresh water derived from inland drainage. Fresh water inflow is limited and is mainly via intermittent streams draining into Baffin Bay, and the Arroyo Colorado and Northern Floodway carrying overflow from the Rio Grande. Its permanent Gulf connections are also limited, being confined to communication via Corpus Christi Bay, a dredged channel opposite Port Mansfield, and the natural Brazos Santiago pass (now artificially maintained) at the southern tip of Padre Island