Cost‐Effective Placement of Best Management Practices in a Watershed: Lessons Learned from Conservation Effects Assessment Project

This article reviews the key, cross‐cutting findings concerning watershed‐scale cost‐effective placement of best management practices (BMPs) emerging from the National Institute of Food and Agriculture Conservation Effects Assessment Project (CEAP) competitive grants watershed studies. The synthesis focuses on two fundamental aspects of the cost‐effectiveness problem: (1) how to assess the location‐ and farmer‐specific costs of BMP implementation, and (2) how to decide on which BMPs need to be implemented and where within a given watershed. Major lessons learned are that (1) data availability remains a significant limiting factor in capturing within‐watershed BMP cost variability; (2) strong watershed community connections help overcome the cost estimation challenges; (3) detailing cost components facilitates the transferability of estimates to alternative locations and/or economic conditions; and (4) implicit costs vary significantly across space and farmers. Furthermore, CEAP studies showed that (5) evolutionary algorithms provide workable ways to identify cost‐effective BMP placements; (6) tradeoffs between total conservation costs and watershed‐scale cost‐effective water quality improvements are commonly large; (7) quality baseline information is essential to solving cost‐effectiveness problem; and (8) systemic and modeling uncertainties alter cost‐effective BMP placements considerably.     

Assessing BMP Effectiveness and Guiding BMP Planning Using Process‐Based Modeling

There is an increasing need for improved process‐based planning tools to assist watershed managers in the selection and placement of effective best management practices (BMPs). In this article, we present an approach, based on the Water Erosion Prediction Project model and a pesticide transport model, to identify dominant hydrologic flow paths and critical source areas for a variety of pollutant types. We use this approach to compare the relative impacts of BMPs on hydrology, erosion, sediment, and pollutant delivery within different landscapes. Specifically, we focus on using this approach to understand what factors promoted and/or hindered BMP effectiveness at three Conservation Effects Assessment Project watersheds: Paradise Creek Watershed in Idaho, Walnut Creek Watershed in Iowa, and Goodwater Creek Experimental Watershed in Missouri. These watersheds were first broken down into unique land types based on soil and topographic characteristics. We used the model to assess BMP effectiveness in each of these land types. This simple process‐based modeling approach provided valuable insights that are not generally available to planners when selecting and locating BMPs and helped explain fundamental reasons why long‐term improvement in water quality of these three watersheds has yet to be completely realized.     

Modeling the Effects of Extreme Drought on Pollutant Transport Processes in the Yangtze River Estuary

Water resources in the Yangtze River Estuary (YRE), which is the vital water supply for Shanghai, decreased by approximately 2.45 Gm³ in 2006, the second‐worst recorded drought year. A numerical model was developed to investigate the effects of this extreme drought on pollutant transport processes in the YRE. The model was calibrated against observations and displayed good agreement. Residence time, a critical hydrodynamic indicator, was implemented to indicate pollutant transport processes. Numerical experiments were conducted to examine the possibly drought‐induced influences. The model results demonstrated that the influences on pollutant transport processes varied spatially and temporally, and these influences could partly explain the observed temporal and spatial variations of total nitrate in 2006. The area most susceptible to drought is in the north branch with 2‐11 days' extension of residence time. As the drought occurred in both the high and normal water periods, its influences were more significant during the normal water period with saltwater intrusion into the north branch. The drought also introduced a pollutant transport lag in timescale of approximately five days by diminishing the seaward advection flux with freshwater discharge. In 2006, the magnified tidal influence during the drought contributed more than usual to structuring pollutant transport, as the pollutant transport processes were intensely associated with tidal flow and tidal cycle.     

Post‐Ike economic resilience along the Texas coast

The economic devastation resulting from recent natural disasters has spawned intense interest in programmes that promote regional resilience. The economic impacts of Hurricane Ike (September 2008) endured long beyond the storm's landfall, compounded by a national recession. This study analyses the pattern of post‐Ike industrial growth in eight coastal counties of Texas, United States, and identifies sources of resilience and potential drivers of recovery. The results indicate that post‐disaster growth patterns differ from established growth patterns. Levels of resilience vary across industrial sectors, and service sectors tend to lead a recovery. The resilience of the hotel and restaurant sector, for instance, suggests that the presence of relief workers might immunise certain sectors against a post‐disaster economic downturn. Besides the sectors that are generally resilient, each county has its own distinct sectors that, depending on the extent of the damage suffered, tend to perform strongly after a disaster, owing to the characteristics of the respective county's economy.     

Measuring disaster recovery: bouncing back or reaching the counterfactual state?

How should one measure the recovery of a locale from a disaster? The measurement is crucial from a public policy and administration standpoint to determine which places should receive disaster assistance, and it affects the performance evaluation of disaster recovery programmes. This paper compares two approaches to measuring recovery: (i) bouncing back to pre‐disaster conditions; and (ii) attaining the counterfactual state. The former centres on returning to normalcy following disaster‐induced losses, whereas the latter focuses on attaining the state, using quasi‐experimental design, which would have existed if the disaster had not occurred. Both are employed here to assess two housing recovery indicators (total new units and their valuations) in Hurricane Katrina‐affected counties (rural and urban). The examination reveals significantly different outcomes for the two approaches: counties have not returned to their pre‐disaster housing conditions, but they do exhibit counterfactual recovery. Moreover, rural counties may not be as vulnerable as assumed in the disaster recovery literature.     

Regional and Temporal Differences in Nitrate Trends Discerned from Long‐Term Water Quality Monitoring Data

Riverine nitrate (NO₃) is a well‐documented driver of eutrophication and hypoxia in coastal areas. The development of the elevated river NO₃ concentration is linked to anthropogenic inputs from municipal, agricultural, and atmospheric sources. The intensity of these sources has varied regionally, through time, and in response to multiple causes such as economic drivers and policy responses. This study uses long‐term water quality, land use, and other ancillary data to further describe the evolution of river NO₃ concentrations at 22 monitoring stations in the United States (U.S.). The stations were selected for long‐term data availability and to represent a range of climate and land‐use conditions. We examined NO₃ at the monitoring stations, using a flow‐weighting scheme meant to account for interannual flow variability allowing greater focus on river chemical conditions. River NO₃ concentration increased strongly during 1945‐1980 at most of the stations and have remained elevated, but stopped increasing during 1981‐2008. NO₃ increased to a greater extent at monitoring stations in the Midwest U.S. and less so at those in the Eastern and Western U.S. We discuss 20th Century agricultural development in the U.S. and demonstrate that regional differences in NO₃ concentration patterns were strongly related to an agricultural index developed using principal components analysis. This unique century‐scale dataset adds to our understanding of long‐term NO₃ patterns in the U.S.     

Hydrological Responses to Climate and Land‐Use Changes along the North American East Coast: A 110‐Year Historical Reconstruction

The North American east coast (NAEC) region experienced significant climate and land‐use changes in the past century. To explore how these changes have affected land water cycling, the Dynamic Land Ecosystem Model (DLEM 2.0) was used to investigate the spatial and temporal variability of runoff and river discharge during 1901‐2010 in the study area. Annual runoff over the NAEC was 420 ± 61 mm/yr (average ± standard deviation). Runoff increased in parts of the northern NAEC but decreased in some areas of the southern NAEC. Annual freshwater discharge from the study area was 378 ± 61 km³/yr (average ± standard deviation). Factorial simulation experiments suggested that climate change and variability explained 97.5% of the interannual variability of runoff and also resulted in the opposite changes in runoff in northern and southern regions of the NAEC. Land‐use change reduced runoff by 5‐22 mm/yr from 1931 to 2010, but the impacts were divergent over the Piedmont region and Coastal Plain areas of the southern NAEC. Land‐use change impacts were more significant at local and watershed spatial scales rather than at regional scales. Different responses of runoff to changing climate and land‐use should be noted in future water resource management. Hydrological impacts of afforestation and deforestation as well as urbanization should also be noted by land‐use policy makers.     

Trophic State in Voyageurs National Park Lakes before and after Implementation of a Revised Water‐Level Management Plan

We compiled Secchi depth, total phosphorus, and chlorophyll a (Chla) data from Voyageurs National Park lakes and compared datasets before and after a new water‐level management plan was implemented in January 2000. Average Secchi depth transparency improved (from 1.9 to 2.1 m, p = 0.020) between 1977‐1999 and 2000‐2011 in Kabetogama Lake for August samples only and remained unchanged in Rainy, Namakan, and Sand Point Lakes, and Black Bay in Rainy Lake. Average open‐water season Chla concentration decreased in Black Bay (from an average of 13 to 6.0 μg/l, p = 0.001) and Kabetogama Lake (from 9.9 to 6.2 μg/l, p = 0.006) between 1977‐1999 and 2000‐2011. Trophic state index decreased significantly in Black Bay from 59 to 51 (p = 0.006) and in Kabetogama Lake from 57 to 50 (p = 0.006) between 1977‐1999 and 2000‐2011. Trophic state indices based on Chla indicated that after 2000, Sand Point, Namakan, and Rainy Lakes remained oligotrophic, whereas eutrophication has decreased in Kabetogama Lake and Black Bay. Although nutrient inputs from inflows and internal sources are still sufficient to produce annual cyanobacterial blooms and may inhibit designated water uses, trophic state has decreased for Kabetogama Lake and Black Bay and there has been no decline in lake ecosystem health since the implementation of the revised water‐level management plan.     

Controls on Temperature in Salmonid‐Bearing Headwater Streams in Two Common Hydrogeologic Settings,Kenai Peninsula,Alaska

Headwater streams are the most numerous in terms of both number and length in the conterminous United States and play important roles as spawning and rearing grounds for numerous species of anadromous fish. Stream temperature is a controlling variable for many physical, chemical, and biological processes and plays a critical role in the overall health and integrity of a stream. We investigated the controls on stream temperature in salmon‐bearing headwater streams in two common hydrogeologic settings on the Kenai Peninsula, Alaska: (1) drainage‐ways, which are low‐gradient streams that flow through broad valleys; and (2) discharge‐slopes, which are high gradient streams that flow through narrow valleys. We hypothesize local geomorphology strongly influences surface‐water and groundwater interactions, which control streamflow at the network scale and stream temperatures at the reach scale. The results of this study showed significant differences in stream temperatures between the two hydrogeologic settings. Observed stream temperatures were higher in drainage‐way sites than in discharge‐slope sites, and showed strong correlations as a continuous function with the calculated topographic metric flow‐weighted slope. Additionally, modeling results indicated the potential for groundwater discharge to moderate stream temperature is not equal between the two hydrogeologic settings, with groundwater having a greater moderating effect on stream temperature at the drainage‐way sites.     

The legacy of migration in response to climate stress: learning from the Gilbertese resettlement in the Solomon Islands

The long‐term threat of sea‐level rise to coral atoll and reef island communities in Kiribati, Tuvalu and other nations has raised the possibility of international migration. Historical resettlements in the Pacific may provide valuable insight into the long‐term effect of future climate change‐related migration on communities. This study evaluates the challenges faced by Gilbertese people resettled from modern‐day Kiribati to Ghizo in the Solomon Islands by the British colonial administration in the mid‐1900s. Drawing upon field interviews (n = 45) conducted in 2011 and the available historical literature, the study examines the circumstances of the initial failed resettlement in the equatorial Phoenix Islands, the subsequent relocation to Ghizo, and the recent concerns of the Gilbertese in Ghizo. Focus is placed on the struggle to recover from the 2007 tsunami that devastated the unprepared community. The analysis reveals that uncertainty about land tenure (raised by 61% of respondents) persists 60 years after resettlement, and is linked to the ability to recover from the tsunami, tensions with the Melanesian population, concerns over political representation, cultural decline, and education and employment opportunities. The Gilbertese experience can serve as a cautionary tale for policymakers considering mechanisms for facilitating climate change‐related migration.