Recent surveys of tropical forest water use suggest that rainfall interception by the canopy is largest in wet maritime locations. To investigate the underlying processes at one such location-the Luquillo Experimental Forest in eastern Puerto Rico-66 days of detailed throughfall and above-canopy climatic data were collected in 1996 and analysed using the Rutter and Gash models of rainfall interception. Throughfall occurred on 80% of the days distributed over 80 rainfall events. Measured interception loss was 50% of gross precipitation. When Penman-Monteith based estimates for the wet canopy evaporation rate (0.11 mm h Ϫ1 on average) and a canopy storage of 1.15 mm were used, both models severely underestimated measured interception loss. A detailed analysis of four storms using the Rutter model showed that optimizing the model for the wet canopy evaporation component yielded much better results than increasing the canopy storage capacity. However, the Rutter model failed to properly estimate throughfall amounts during an exceptionally large event. The analytical model, on the other hand, was capable of representing interception during the extreme event, but once again optimizing wet canopy evaporation rates produced a much better fit than optimizing the canopy storage capacity. As such, the present results support the idea that it is primarily a high rate of evaporation from a wet canopy that is responsible for the observed high interception losses. ᭧ 1999 Elsevier Science B.V. All rights reserved.

Since the Brisbane Declaration in 2007, implementation of environmental flows in public policies has witnessed a steady increase around the globe. Environmental water reserves are an annual volume that is designated to remain in the ecosystem for the sustainable management of river basins. In Mexico, these reserves are determined on the basis of the Mexican Environmental Flows Norm and must be established at a river basin scale through a presidential decree for 50 years. In this manuscript, we present and discuss the implementation strategy of the norm developed for the National Water Reserves for the Environment Program, and its results in 25 reference sites based on environmental flow assessments conducted from 2012 to 2015 using hydrological and holistic methodologies. An analytical evaluation revealed an overall consistency between the Norm's environmental objectives (baseline) and the current ecological conditions on‐site for the 80% of the cases (96% over high confidence rating). Furthermore, in 72% of the reference sites, the coefficient of variation among the reserve's was below the fourth quartile (<11%), whereas those remaining above that limit can be attributed to a difference in the methods' hydrologic scope. The recommended volumes for environmental allocation are feasible under the current water availability conditions in the 94% of the river basins. Although challenges have appeared in the process, to date, one reserve has been decreed on the basis of the strategic approach of setting sustainable limits of water allocation and being built an enriched flow‐ecology relationships' understanding system, urgently needed to prevent ecosystems degradation and secure ecological processes.

Abstract. A number of large hydropower dams are currently under development or in an advanced stage of planning in the Magdalena River basin, Colombia, spelling uncertainty for the Mompós Depression wetlands, one of the largest wetland systems in South America at 3400 km 2 . Annual large-scale inundation of floodplains and their associated wetlands regulates water, nutrient, and sediment cycles, which in turn sustain a wealth of ecological processes and ecosystem services, including critical food supplies. In this study, we implemented an integrated approach focused on key attributes of ecologically functional floodplains: (1) hydrologic connectivity between the river and the floodplain, and between upstream and downstream sections; (2) hydrologic variability patterns and their links to local and regional processes; and (3) the spatial scale required to sustain floodplain-associated processes and benefits, like migratory fish biodiversity. The implemented framework provides an explicit quantification of the nonlinear or direct response relationship of those considerations with hydropower development. The proposed framework was used to develop a comparative analysis of the potential effects of the hydropower expansion necessary to meet projected 2050 electricity requirements. As part of this study, we developed an enhancement of the Water Evaluation and Planning system (WEAP) that allows resolution of the floodplains water balance at a medium scale (∼ 1000 to 10 000 km 2 ) and evaluation of the potential impacts of upstream water management practices. In the case of the Mompós Depression wetlands, our results indicate that the potential additional impacts of new hydropower infrastructure with respect to baseline conditions can range up to one order of magnitude between scenarios that are comparable in terms of energy capacity. Fragmentation of connectivity corridors between lowland floodplains and upstream spawning habitats and reduction of sediment loads show the greatest impacts, with potential reductions of up to 97.6 and 80 %, respectively, from pre-dam conditions. In some development scenarios, the amount of water regulated and withheld by upstream infrastructure is of similar magnitude to existing fluxes involved in the episodic inundation of the floodplain during dry years and, thus, can also induce substantial changes in floodplain seasonal dynamics of average-to-dry years in some areas of the Mompós Depression.

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