Predicting Maximum Lake Depth from Surrounding Topography

Information about lake morphometry (e.g., depth, volume, size, etc.) aids understanding of the physical and ecological dynamics of lakes, yet is often not readily available. The data needed to calculate measures of lake morphometry, particularly lake depth, are usually collected on a lake-by-lake basis and are difficult to obtain across broad regions. To span the gap between studies of individual lakes where detailed data exist and regional studies where access to useful data on lake depth is unavailable, we developed a method to predict maximum lake depth from the slope of the topography surrounding a lake. We use the National Elevation Dataset and the National Hydrography Dataset – Plus to estimate the percent slope of surrounding lakes and use this information to predict maximum lake depth. We also use field measured maximum lake depths from the US EPA's National Lakes Assessment to empirically adjust and cross-validate our predictions. We were able to predict maximum depth for ∼28,000 lakes in the Northeastern United States with an average cross-validated RMSE of 5.95 m and 5.09 m and average correlation of 0.82 and 0.69 for Hydrological Unit Code Regions 01 and 02, respectively. The depth predictions and the scripts are openly available as supplements to this manuscript

Using GIS to Estimate Lake Volume from Limited Data

<p>Presentation given at North American Lake Managment Society 2009 Annual meeting</p

Estimating Summer Nutrient Concentrations in Northeastern Lakes from SPARROW Load Predictions and Modeled Lake Depth and Volume

<div><p>Global nutrient cycles have been altered by the use of fossil fuels and fertilizers resulting in increases in nutrient loads to aquatic systems. In the United States, excess nutrients have been repeatedly reported as the primary cause of lake water quality impairments. Setting nutrient criteria that are protective of a lakes ecological condition is one common solution; however, the data required to do this are not always easily available. A useful solution for this is to combine available field data (i.e., The United States Environmental Protection Agency (USEPA) National Lake Assessment (NLA)) with average annual nutrient load models (i.e., USGS SPARROW model) to estimate summer concentrations across a large number of lakes. In this paper we use this combined approach and compare the observed total nitrogen (TN) and total phosphorus (TN) concentrations in Northeastern lakes from the 2007 National Lake Assessment to those predicted by the Northeast SPARROW model. We successfully adjusted the SPARROW predictions to the NLA observations with the use of Vollenweider equations, simple input-output models that predict nutrient concentrations in lakes based on nutrient loads and hydraulic residence time. This allows us to better predict summer concentrations of TN and TP in Northeastern lakes and ponds. On average we improved our predicted concentrations of TN and TP with Vollenweider models by 18.7% for nitrogen and 19.0% for phosphorus. These improved predictions are being used in other studies to model ecosystem services (e.g., aesthetics) and dis-services (e.g. cyanobacterial blooms) for ~18,000 lakes in the Northeastern United States. </p> </div

Biotic interactions and community dynamics in the semiarid thorn scrub of Bosque Fray Jorge National Park, north-central Chile: A paradigm revisited

In 1989, we initiated a long-term field experiment in a semiarid thorn scrub community in north-central Chile. We posited that biotic interactions, particularly predation, interspecific competition, and herbivory assumed a primary top-down role in affecting small mammals and annual plants here. Using a multi-factorial design we selectively excluded vertebrate predators (principally carnivores and raptors) and a large small mammal herbivore, the degu (Octodon degus), from replicated 0.56 ha exclosures located in a valley near the coast in Bosque Fray Jorge National Park. Evidence initially supported effects of predator exclusion on O. degus but not for other small mammals in the assemblage (e.g., Phyllotis darwini, Abrothrix olivaceus). Subsequent years of monitoring have documented that predation has temporary effects on degu numbers, but that populations of this and other small mammals are much more strongly influenced by environmental bottom-up factors (i.e., rainfall). Further, our experimental manipulation has provided no evidence for negative interspecific competition effects on numbers of any small mammal in this assemblage. Degu exclusions, however, have had negative indirect effects on exotic annuals; native annuals appear to outcompete exotics especially during drought years The effect is magnified in all-small mammal exclusions. Since about 2002, selective exclusions of lagomorphs and small mammals have resulted in changes in cover of some perennial shrubs. Also notable has been a fundamental shift in the small mammal composition following the last major El Niño Southern Oscillation (ENSO) event in 2000?2002; degus now comprise a majority of small mammal biomass in the assemblage, and their numbers have become more stable and less temporally variable. This appears to have been caused by a shift in rainfall periodicity from strong interannual fluctuations in response to periodic ENSOs, to a more equitable pattern with more consistent annual rainfall. This represents one of the first documented cases of system-wide biotic phase shifts to a relatively modest change in rainfall regime. This may be indicative of ongoing climate change in the Chilean semiarid region, and we expect that further changes in the community will occur if those trends continue.Fil: Meserve, Peter L.. University of Illinois; Estados UnidosFil: Kelt, Douglas A.. University of California; Estados UnidosFil: Gutiérrez, Julio R.. Universidad de La Serena; ChileFil: Previtali, Maria Andrea. Universidad Nacional del Litoral. Facultad de Humanidades y Ciencias. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Milstead, W. Bryan. U.S. Environmental Protection Agency; Estados Unido

Global climate change and small mammal populations in north-central Chile

Desde 1989, hemos estudiado las poblaciones de micromamíferos en un sitio semiárido en el norte de Chile, mediante un complejo de grillas de trampeo-vivo a gran escala. La exclusión selectiva de depredadores vertebrados y/o posibles competidores micromamíferos ha resultado en efectos peque-ños y/o mayormente transitorios en la dinámica de micromamiferos y en la compositión de la comunidad de plantas. Durante el período de estudio, han habido 5 eventos lluviosos o El Niño con duratión de 1 a 3 años. Los micromamíferos residentes o centrales tales como Abrothrix olivaceus, Phyllotis darwini, y Octodon degus mostraron marcadas fluctuaciones durante y posteriormente a los pulsos de lluvias. Las especies oportunistas o de residencia transitoria tales como Oligoryzomys longicaudatus y A. longipilis desaparecen del ambiente de matorral espinoso por períodos variables de tiempo. Todas las especies persisten en ambientes cercanos más mésicos asociados a lechos de arroyos secos (aguadas). Después de 3 años lluviosos consecutivos entre el 2000 y 2002, el promedio anual de precipitaciones ha aumentado en esta región, principalmente debido a una ausencia de sequías prolongadas. Bajo estas condiciones y usando un modelo cualitativo propuesto por Noy-Meir, especies de larga vida pueden llegar a ser más abundantes. Los cambios del ensamble de micromamíferos son consistentes con estas predicciones, el roedor caviomorfo con una historia de vida larga, O. degus, ahora constituye una proporción más constante de la biomasa de micromamíferos del matorral espinoso, y ha habido una reductión en la variatión de la diversidad de especies. El aumento en las lluvias, que está pronosticado como una consecuencia del cambio climático global para esta región, puede estar causando cambios en la estructura y composición del ensamble de micromamíferos, y eventualmente resultará en un ensamble más estable y menos fluctuante en el matorral espinoso. A su vez, los grupos invasores como los lagomorfos y plantas efímeras introducidas pueden intensificar su establecimiento en esta comunidad. Por lo tanto, las consecuencias a largo plazo de los cambios en los patrones de lluvias debidos a El Niño Oscilación del Sur (ENOS) con importantes teleconexiones a fenómenos de escala global, causarán aquí cambios diversos al nivel de la comunidad.Since 1989 we have monitored small mammal populations at a semiarid site in north-central Chile with a large-scale livetrapping grid complex. Selective exclusions of vertebrate predators or putative small mammal competitors, or both, have yielded relatively small or mostly transitory effects, or both, on small mammal population dynamics and plant community composition. During the study period 5 El Niohigh rainfall episodes have occurred lasting 13 years. Resident or core small mammals such as Abrothrix olivaceus, Phyllotis darwini, and Octodon degus experience dramatic fluctuations during and following rainfall pulses. Temporary resident or opportunistic species such as Oligoryzomys longicaudatus and A. longipilis disappear from the thorn scrub for varying periods of time. All species persist in more mesic nearby habitats near dry stream courses (aguadas). Since a 3-year high rainfall event in 20002002 mean annual rainfall has increased in this region, mainly due to a lack of prolonged droughts. Under these conditions, and building on a qualitative model proposed by Noy-Meir, long-lived species might become more abundant. Changes in the small mammal assemblage are consistent with these predictions; O. degus, a caviomorph rodent with a long life span, now comprises a more constant proportion of the small mammal biomass in the thorn scrub, and we have documented reduced variation in species diversity. Increased rainfall, a predicted consequence of global climate change in this region, might be leading to changes in small mammal assemblage structure and composition and ultimately will result in a more stable, less oscillatory assemblage in the thorn scrub. Additionally, invasive groups such as introduced lagomorphs and ephemeral plants might become more abundant in this community. The long-term consequences of changes in rainfall patterns due to El Nio Southern Oscillations (ENSOs), with important teleconnections to global-scale phenomena, will lead to diverse changes at the community level here.Fil: Meserve, Peter L.. University of Illinois; Estados UnidosFil: Kelt, Douglas A.. University of California; Estados UnidosFil: Previtali, Maria Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Cary Institute of Ecosystem Studies; Estados UnidosFil: Milstead, W. Bryan. United States Environmental Protection Agency; Estados UnidosFil: Gutiérrez, Julio R.. Universidad de La Serena; Chil

Adjusted (Vollenweider Model) total nitrogen (A) and phosphorus (B) in Northeast Lakes.

<p>National Lake Assessment observed 2007 summer concentrations of (A) total nitrogen and (B) phosphorus in Northeast Lakes versus the Vollenweider (Vw) adjusted average annual SPARROW predicted concentrations. Robust non-linear regression was used to fit SPARROW predictions to 2007 NLA observations using the Vollenweider equation (H₆). Observations are color coded by hydraulic residence time (HRT: Short < 0.04 years; Medium = 0.04 to 0.4 years; Long > 0.4 years). TN = Total Nitrogen. TP = Total Phosphorus.</p

Map of the study area.

<p>Shown are the locations of the lakes within Hydrologic Unit Code (HUC) regions 01 (New England) and 02 (Mid-Atlantic).</p

The geographical distribution of the Northeast lakes coded by trophic state.

<p>The National Lake Assessment Lake centroids with trophic state (TS) estimated from observed total (A) Nitrogen and (B) Phosphorus concentrations. Lakes with trophic state estimated from the Vollenweider adjusted predicted total (C) nitrogen and (D) phosphorus concentrations. </p

Total nitrogen (A) and phosphorus (B) in Northeast Lakes.

<p>National Lake Assessment 2007 observed summer concentrations versus the average annual SPARROW predicted concentrations. Observations are color coded by hydraulic residence time (HRT: Short < 0.04 years; Medium = 0.04 to 0.4 years; Long > 0.4 years). TN = Total Nitrogen. TP = Total Phosphorus.</p