Simulating the water budget of a Prairie Potholes complex from LiDAR and hydrological models in North Dakota,USA

Abstract

Hydrological processes of the wetland complex in the Prairie Pothole Region (PPR) are difficult to model, partly due to a lack of wetland morphology data. We used Light Detection And Ranging (LiDAR) data sets to derive wetland features; we then modelled rainfall, snowfall, snowmelt, runoff, evaporation, the “fill-and-spill” mechanism, shallow groundwater loss, and the effect of wet and dry conditions. For large wetlands with a volume greater than thousands of cubic metres (e.g. about 3000 m³), the modelled water volume agreed fairly well with observations; however, it did not succeed for small wetlands (e.g. volume less than 450 m³). Despite the failure for small wetlands, the modelled water area of the wetland complex coincided well with interpretation of aerial photographs, showing a linear regression with R² of around 0.80 and a mean average error of around 0.55 km². The next step is to improve the water budget modelling for small wetlands.

Editor Z.W. Kundzewicz; Associate editor X. Chen

Citation Huang, S.L., Young, C., Abdul-Aziz, O.I., Dahal, D., Feng, M., and Liu, S.G., 2013. Simulating the water budget of a Prairie Potholes complex from LiDAR and hydrological models in North Dakota, USA. Hydrological Sciences Journal, 58 (7), 1434–1444.     

Scaling of transient wave–soil interaction problems

Within the framework of compressible multi‐phase flow through deformable porous media, wave–soil interactions in the near‐shore region during wave runup and drawdown are modeled. Critical non‐dimensional parameters governing the interaction processes are identified. Within the context of wave basin and centrifuge wave tank facilities, we propose scaling relations for the experimental investigations of the transient and steady‐state responses of wave–soil systems. Numerical simulations are conducted to illustrate and confirm the theoretical and scaling analyses. Based on the simulations results, the implications on the design of experiments and interpretation of results are discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

The circulation and hydrography of conception bay,Newfoundland

Abstract

The hydrography and circulation of Conception Bay (Newfoundland) are described based on hydrographic, current‐meter and drifter data collected over four years (1988–1991). The seasonal cycles of temperature (‐1.6 to 13–17°C) and salinity (31–32.5) in the bay closely follow those on the adjacent shelf. Exchange of bottom water was observed in April 1989. Deepwater exchange was observed from late fall to early winter of 1989–90. Tidal currents are weak, 1–2 cm s^‐1 for the M₂ and K₁ constituents. Observed Eulerian mean currents (<3 cm s^‐1) are smaller than the standard deviation (1–11 cm s^‐1); however, there is a persistent outflowing current of 10 to 20 cm s^‐1 within 2 km of the shoreline on the eastern side of the outer bay. The Lagrangian correlation length scale is from 4 to 10 km, in agreement with the weak coherence squared (≤0.4) found between the fixed current‐meter sites separated by greater than 4–5 km. The variable currents (up to 20 cm s^‐1) tend to be cyclonic. Cyclonic eddies were observed near the mouth on the eastern side of the bay, adjacent to the outflow. A simplified fractal dispersion model gives residence times of 42 d similar to those obtained from a scaling analysis (30–40 d) and a diagnostic numerical model (30 d).     

Traces of dissolved particles,including coccoliths,in the tests of agglutinated foraminifera from the Challenger Deep (10,897 m water depth,western equatorial Pacific)

We examined four multilocular agglutinated foraminiferan tests from the Challenger Deep, the deepest point in the world's oceans and well below the depth at which biogenic and most detrital minerals disappear from the sediment. The specimens represent undescribed species. Three are trochamminaceans in which imprints and other traces of dissolved agglutinated particles are visible in the orange or yellowish organic test lining. In Trochamminacean sp. A, a delicate meshwork of organic cement forms ridges between the grain impressions. The remnants of test particles include organic structures identifiable as moulds of coccoliths produced by the genus Helicosphaera. Their random alignment suggests that they were agglutinated individually rather than as fragments of a coccosphere. Trochamminacean sp. C incorporates discoidal structures with a central hole; these probably represent the proximal sides of isolated distal shields of another coccolith species, possibly Hayaster perplexus. Imprints of planktonic foraminiferan test fragments are also present in both these trochamminaceans. In Trochamminacean sp. B, the test surface is densely pitted with deep, often angular imprints ranging from roughly equidimensional to rod-shaped. The surfaces are either smooth, or have prominent longitudinal striations, probably made by cleavage traces. We presume these imprints represent mineral grains of various types that subsequently dissolved. X-ray microanalyses reveal strong peaks for Ca associated with grain impressions and coccolith remains in Trochamminacean sp. C. Minor peaks for this element are associated with coccolith remains and planktonic foraminiferan imprints in Trochamminacean sp. A. These Ca peaks possibly originate from traces of calcite remaining on the test surfaces. Agglutinated particles, presumably clay minerals, survive only in the fourth specimen (‘Textularia’ sp.). Here, the final 4–5 chambers comprise a pavement of small, irregularly shaped grains with flat surfaces and no obvious intervening cement. Our observations suggest that (1) small biogenic particles can reach the deepest parts of the ocean intact in rapidly sinking phytodetrital aggregates or faecal pellets and (2) some agglutinated foraminifera living at extreme hadal depths construct a test from biogenic or detrital particles, which subsequently dissolve, leaving imprints and other remnants in the organic matrix of the test.     

Salmon aquaculture and coastal ecosystem health in Chile: Analysis of regulations,environmental impacts and bioremediation systems

In 2007 salmon, mollusk and seaweed aquaculture production in Chile totaled 904 thousand tonnes, making the nation the leading marine aquaculture producer in the western world. Salmonids grown in open cage net pens account for over 73% of the production. This review summarizes the current status of Chilean aquaculture and proposes the establishment of new regulations and monitoring programmes that encourage and accommodate emerging bioremediation technologies. In contrast to a rapidly expanding, well-financed and technologically advanced industry, the regulatory structure in Chile is outdated and based on insufficient science. The number of publications on the environmental impacts of salmon aquaculture in Chile is low relative to its production level. Nevertheless, the impacts of organic and inorganic waste on benthic communities, pelagic organisms and bird populations are documented. The technology to reduce these impacts using integrated multi-trophic aquaculture (IMTA) strategies exists, but has not been implemented at commercial scales. We call on the government and industry to support the creation of a well-financed and politically independent agency responsible for developing and enforcing science-based environmental regulations in Chile. The agency's immediate goal should be to fund research required to develop a transparent, ecosystem-based regulatory framework that promotes IMTA. Monitoring programs and licensing procedures must consider the impacts of individual sites and the cumulative impacts from multiple sites across a wide range of spatial scales. Before such changes are realized, environmental threats and human health risks will remain unacceptably high and salmon farming in Chile will not meet any reasonable definition of sustainability.     

Varve and radiocarbon dating support the rapid advance of Jakobshavn Isbræ during the Little Ice Age

Large outlet glaciers draining the Greenland Ice Sheet significantly influence overall ice sheet mass balance. Considerable short term (years to decades) retreat and fluctuations in velocity of Jakobshavn Isbræ, western Greenland, illustrate the complex nature by which large outlet glaciers respond to climate change, making predictions of future ice sheet change challenging. To provide a longer-term view (centuries), we investigate the geological record of Jakobshavn Isbræ change. We use continuous sediment records from lakes that were influenced by the recent advance of Jakobshavn Isbræ, which took place during the Little Ice Age. In particular, we explore the use of annually laminated lake sediments (varves) to precisely constrain the advance of the ice margin as it approached its late Holocene maximum extent. We find that the ice margin advanced recently, at least after ～1650 to ～1700 AD, and more likely ～1800 AD. We suggest that during this period Jakobshavn Isbræ advanced at a rate that was similar to its historically documented average retreat since ～1850 AD. Our results indicate that Jakobshavn Isbræ, and presumably other large marine calving glaciers, have the ability to advance quickly in response to climate forcing.     

Total Earth Pressure Cells for Measuring Loads in a Municipal Solid Waste Landfill

Commercially available hydraulic total overburden pressure cells were installed in the sand drainage layer of a municipal solid waste landfill and monitored for a period of 3,110 days. Both overburden pressure and temperature were measured in the landfill as it was filled with compacted waste. Topographic surveys of the landfill were periodically conducted to measure the height of waste above the pressure cells and to determine the landfill volume for indirect unit weight estimation. The average ratio of measured to theoretically-predicted overburden pressure was 0.6, indicating that on average the pressure cells underestimated the load. The overburden pressure measured near the toe of the landfill was greater than that predicted by the unit weight of landfilled material, while most of the overburden pressure measurements further inside the landfill were less than predicted. Several possible causes for this phenomenon are discussed, including the uneven distribution of forces resulting from the heterogeneous nature of the waste and cover soil. The earth pressure cells were capable of detecting the placement of individual waste lifts.