A reconnaissance approach for hydrology of atoll lagoons

Abstract

As a reconnaissance tool of the hydrology of atoll lagoons in the micro-tidal environment of the Tuamotu Archipelago, we define and compute "potential" flow rates at lagoon scale under three swell regimes (high, average, and low swell) after assessment of orientation and width of reef-flat spillways using satellite images. As a direct test, the "potential" flows were compared with field measurements of (1) measured inflows across the reef flat (for eight atolls), (2) net outgoing flow through the pass (for three atolls), and (3) lagoon-level variation rates (for four atolls). Absolute values of "potential" and field flows agreed (r ²=0.94, n=42, slope ~1). Computed average water renewal times (T_RAV) were also tested against concentrations of dissolved organic matter (DOM). DOM and T_RAV were positively correlated (r ²=0.54, n=26; Spearman's r_s=0.54), and this relationship should enable the detection of unusual atolls. This approach would then appear to be useful for the reconnaissance of hydrodynamics processes in comparable micro-tidal environments.