Reference conditions for restoring an estuary at the mouth of the Colorado River : Tijuana Estuary and the shelly record at Isla Montague

Abstract

Restoration of the Colorado River Estuary currently faces three primary challenges: a) the need for increased freshwater input, b) the need for increased river-sea connectivity, and c) the need for comprehensive reference conditions, in order to articulate robust and reasonable restoration goals. While recent efforts have addressed the first two challenges, via the delivery of surface flows allocated for restoration from the Colorado River and the dredging of channels, reference criteria are still needed. This thesis explores two references, namely past ecological conditions from the estuary itself in the form of the benthic shelly record, and current ecological conditions and management techniques from a similar site, Tijuana Estuary. Best management practices are derived from each reference. The need to maintain river-sea connectivity, in order to restore estuarine conditions is emphasized. It is recommended that restoration at Colorado River Estuary adopt an adaptive approach to management, allowing for flexibility while creating opportunity for further research, and emphasize functional goals that account for the dynamism of nature and the pervasive influence of contemporary human contexts.