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[1] Long-and short-term changes in the spatial distribution of surface water phosphorus concentrations were assessed for the Everglades wetland (USA) from 12 years of monitoring data. Changes in phosphorus spatial distributions, before and after implementation of measures to reduce phosphorus, including stormwater treatment areas (STAs) and best management practices (BMPs), were used to evaluate the effect of the remediation strategies in the naturally oligotrophic wetland. Results showed a clear spatial and temporal gradient in phosphorus concentrations, with highest total phosphorus (TP) reaching 200 mg/L in the northern Water Conservation Areas (WCAs) because of canal inflow from the Everglades Agricultural Area (EAA). Long-term records of TP concentrations from 1995 to 2007 showed declines in Water Conservation Area WCA1 during the dry season (À5.1%). Short-term changes (2003)(2004)(2005)(2006)(2007) showed increasing trends in TP concentrations elsewhere in the Everglades, mainly in the southern areas: WCA3 and Everglades National Park (ENP). From 2003 to 2007, phosphorus increased by 7.4% per year in the ENP during the dry season. The area of the Everglades that exceeded the 10 mg/L surface water TP concentration ecological threshold was quantified and showed a long-term overall decline. However, except for the ENP, more than 65% of the Everglades surface area exceeded the 10 mg/L water quality threshold in 2007. During recent years, ENP and WCA3 surface areas that exceeded the alternative 15 mg/L annual geometric mean slightly increased, confirming the need to closely monitor these two regions.

The critical zone (CZ) can be conceptualized as an open system reactor that is continually transforming energy and water fluxes into an internal structural organization and dissipative products. In this study, we test a controlling factor on water transit times (WTT) and mineral weathering called Effective Energy and Mass Transfer (EEMT). We hypothesize that EEMT, quantified based on local climatic variables, can effectively predict WTT within-and mineral weathering products from-the CZ. This study tests whether EEMT or static landscape characteristics are good predictors of WTT, aqueous phase solutes, and silicate weathering products. Our study site is located around Redondo Peak, a rhyolitic volcanic resurgent dome, in northern New Mexico. At Redondo Peak, springs drain slopes along an energy gradient created by differences in terrain aspect. This investigation uses major solute concentrations, the calculated mineral mass undergoing dissolution, and the age tracer tritium and relates them quantitatively to EEMT and landscape characteristics. We found significant correlations between EEMT, WTT, and mineral weathering products. Significant correlations were observed between dissolved weathering products (Na 1 and DIC), 3 H concentrations, and maximum EEMT. In contrast, landscape characteristics such as contributing area of spring, slope gradient, elevation, and flow path length were not as effective predictive variables of WTT, solute concentrations, and mineral weathering products. These results highlight the interrelationship between landscape, hydrological, and biogeochemical processes and suggest that basic climatic data embodied in EEMT can be used to scale hydrological and hydrochemical responses in other sites.

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This study investigates the influence of water, carbon, and energy fluxes on solute production and transport through the Jemez Critical Zone (CZ) and impacts on C‐Q relationships over variable spatial and temporal scales. Chemical depletion‐enrichment profiles of soils, combined with regolith thickness and groundwater data indicate the importance to stream hydrochemistry of incongruent dissolution of silicate minerals during deep bedrock weathering, which is primarily limited by water fluxes, in this highly fractured, young volcanic terrain. Under high flow conditions (e.g., spring snowmelt), wetting of soil and regolith surfaces and presence of organic acids promote mineral dissolution and provide a constant supply of base cations, Si, and DIC to soil water and groundwater. Mixing of waters from different hydrochemical reservoirs in the near stream environment during “wet” periods leads to the chemostatic behavior of DIC, base cations, and Si in stream flow. Metals transported by organic matter complexation (i.e., Ge, Al) and/or colloids (i.e., Al) during periods of soil saturation and lateral connectivity to the stream display a positive relationship with Q. Variable Si‐Q relationships, under all but the highest flow conditions, can be explained by nonconservative transport and precipitation of clay minerals, which influences long versus short‐term Si weathering fluxes. By combining measurements of the CZ obtained across different spatial and temporal scales, we were able to constrain weathering processes in different hydrological reservoirs that may be flushed to the stream during hydrologic events, thereby informing C‐Q relationships.

We investigated vegetation structure, water partitioning dynamics and vegetation greening from 2000 through 2012 in three catchments draining north and east aspects of Redondo Peak in northern New Mexico. Vegetation structure was quantified from 1‐m lidar data, while vegetation greening was quantified using remotely sensed normalized difference vegetation index (NDVI). Hydrological partitioning at the catchment scale was estimated with a metric of catchment‐scale water fluxes and vegetation water use [Horton index (HI)]. The predominantly north‐facing catchment, when compared with the other two eastern catchments, receives less solar radiation, exhibits less forest cover and smaller biomass and has more surface run‐off (~15% of P) as a consequence of a smaller vaporization (85% of P) and smaller vegetation water consumption (HI = 0·85). Moreover, the north‐facing catchment showed smaller peak NDVI values (5·98) and shorter growing season length (121 days) as a consequence of energy limitation. In contrast, the two eastern catchments receive larger solar radiation and have more biomass and forest cover (>76%), smaller surface run‐off (<10% P) and higher vaporization (>90% P) and vegetation water consumption (HI = 0·95). The eastern catchments had larger vegetation greening (6·28–6·58) and a longer growing season (148–160 days). Snowpack conditions, such as maximum snow water equivalent and duration of the snow on the ground, explain over 95% of water partitioning (HI) that in turn influenced annual vegetation greening (R2 = 0·48–0·67; p < 0·05). This catchment‐scale study in perennial streams indicates that terrain aspect at a similar altitude (2700–3435 m) strongly controls energy, water distribution and vegetation productivity in high‐elevation ecosystems. Copyright © 2015 John Wiley & Sons, Ltd.

Proposed hydropower dams at more than 350 sites throughout the Amazon require strategic evaluation of trade-offs between the numerous ecosystem services provided by Earth’s largest and most biodiverse river basin. These services are spatially variable, hence collective impacts of newly built dams depend strongly on their configuration. We use multiobjective optimization to identify portfolios of sites that simultaneously minimize impacts on river flow, river connectivity, sediment transport, fish diversity, and greenhouse gas emissions while achieving energy production goals. We find that uncoordinated, dam-by-dam hydropower expansion has resulted in forgone ecosystem service benefits. Minimizing further damage from hydropower development requires considering diverse environmental impacts across the entire basin, as well as cooperation among Amazonian nations. Our findings offer a transferable model for the evaluation of hydropower expansion in transboundary basins.

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