Terrestrial protected areas maintain freshwater ecosystem resilience to costly aquatic invasive species in the Panama Canal

River damming is expected to proliferate across Tropical American Rivers in the forthcoming decades with expected declines in ecosystem health to costly invasive species. Historical data and modern aquatic plant surveys of one of the largest and oldest tropical dam projects (the > 100 years old Panama Canal) reveal that modern plant communities in areas adjacent to terrestrial Natural Protected Areas (tNPAs) retain a pre-damming community structure that is apparently more resistant to invasive species. Establishing tNPAs adjacent to impounded rivers could be a cost-effective nature-based solution for tropical reservoir management.

Longitudinal, Lateral, Vertical, and Temporal Thermal Heterogeneity in a Large Impounded River: Implications for Cold-Water Refuges

Dam operations can affect mixing of the water column, thereby influencing thermal heterogeneity spatially and temporally. This occurs by restricting or eliminating connectivity in longitudinal, lateral, vertical, and temporal dimensions. We examined thermal heterogeneity across space and time and identified potential cold-water refuges for salmonids in a large impounded river in inland northwestern USA. To describe these patterns, we used thermal infrared (TIR) imagery, in situ thermographs, and high-resolution, 3-D hydraulic mapping. We explained the median water temperature and probability of occurrence of cool-water areas using generalized additive models (GAMs) at reach and subcatchment scales, and we evaluated potential cold-water refuge occurrence in relation to these patterns. We demonstrated that (1) lateral contributions from tributaries dominated thermal heterogeneity, (2) thermal variability at confluences was approximately an order of magnitude greater than of the main stem, (3) potential cold-water refuges were mostly found at confluences, and (4) the probability of occurrence of cool areas and median water temperature were associated with channel geomorphology and distance from dam. These findings highlight the importance of using multiple approaches to describe thermal heterogeneity in large, impounded rivers and the need to incorporate these types of rivers in the understanding of thermal riverscapes because of their limited representation in the literature.

Stability of control of impounded river reaches

<div> <div> <div>Climate change and economic growth place increasing demands on the management of regional and national waterways. These serve both as part of the drainage network of the catchment and as transport route for raw materials and finished goods. These waterways are often impounded rivers where the management of the weirs must serve both shipping and flood protection. For efficient and effective operation purely local control is no longer sufficient. The flow in these rivers is governed by a pair of nonlinear partial differential equations known as the Saint Venant equations. While there are many possible approaches to the design of a computer control system for such a network, all approaches need to include a test of the stability of the system. Here we apply a test is based on a simplified system model to a series of river reaches separated by weirs. This is used to explore different controller settings. These settings are then used to control a full nonlinear computer model of the river. In this way the sensitivity to deviations from the assumed state around which the linearization is carried out is explored.</div> </div> </div>

EVALUATING THE SUSTAINABILITY OF IMPOUNDED RIVERS: AN ECOSYSTEM SERVICES APPROACH

There has been increasing demand in Canterbury, New Zealand for the abstraction of water from rivers. This demand has led to the increased interest in dam projects. But, while river impoundment can result in significant benefits, it also can come at "cost", especially to river ecology. Given these benefits and costs, it is essential that impounded rivers are systematically evaluated for their sustainability. In this paper the ecosystem services approach is applied for the purposes of evaluating the sustainability of the Opihi River located in South Canterbury. Indicators are used to represent the set of ecosystem services provided by the river. Both the criteria of weak and strong sustainability are evaluated in a novel way. Weak and strong sustainability are operationalised through an ecosystem services index and the safe minimum standard concept, respectively. In applying these evaluation methods it is observed that since the construction of the Opuha Dam, the Opihi River has progressed towards weak and strong sustainability.