A method to assess the freshwater inflow requirements of estuaries and application to the Mtata estuary, South Africa     

J. B. Adams  G. C. Bate  T. D. Harrison  P. Huizinga  S. Taljaard  L. van Niekerk  E. E. Plumstead  A. K. Whitfield  T. H. Wooldridge 《Estuaries and Coasts》2002,25(6):1382-1393

The National Water Act (Act 36 of 1998) in South Africa recognizes basic human water requirements as well as the need to sustain the country's freshwater and estuarine ecosystems in a healthy condition for present as well as future generations. In this Act, provision is made for a water reserve to be estimated prior to the authorization of water use (e.g., for agriculture, large volume residential and industrial uses) through licensing. This reserve is the water required to satisfy basic human needs (i.e., 25 1 person^?1 d^?1) and to protect aquatic ecosystems to ensure present and future sustainable use of the resource. This led the Departments of Water Affairs and Forestry and estuarine scientists throughout South Africa to develop a method to determine the freshwater inflow requirements of estuaries. The method includes documenting the geographical boundaries of the estuary and determining estuarine health by comparing the present state of the estuary with a predicted reference condition with the use of an Estuarine Health Index. The importance of the estuary as an ecosystem is taken from a national rating system and together with the present health is used to set an Ecological Reserve Category for the estuary. This category represents the level of protections afforded to an estuary. Freshwater is then reserved to maintain the estuary in that Ecological Reserve Category. The Reserve, the quantity and quality of freshwater required for the estuary, is determined using an approach where realistic future river runoff scenarios are assessed, together with data for present state and reference conditions, to evaluate the extent to which abiotic and biotic conditions within an estuary are likely to vary with changes in river inflow. Results from these evaluations are used to select an acceptable river flow scenario that represents the highest reduction in freshwater inflow that will still protect the aquatic ecosystem of the estuary and keep it in the desired Ecological Reserve Category. The application of the Reserve methodology to the Mtata estuary is described.  相似文献   

Wind tunnel measurement of boundary-layer response to sediment transport   总被引：3，自引：0，他引：3  

Cheryl McKenna Neuman  Marianne Maljaars 《Boundary-Layer Meteorology》1997,84(1):67-83

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Diets of short-tailed shearwaters in the southeastern Bering Sea     

George L. Hunt  Jr.  Cheryl Baduini  Jaime Jahncke 《Deep Sea Research Part II: Topical Studies in Oceanography》2002,49(26)

In the late 1990s, the southeastern Bering Sea exhibited a number of anomalous conditions, including a major die-off of short-tailed shearwaters (Puffinus tenuirostris), a trans-equatorial migrant that constitutes a major portion of the marine bird biomass in the southeastern Bering Sea. As part of a larger study of the ecological role of the inner or structural front over the southeastern Bering Sea shelf, in 1997–1999, we collected short-tailed shearwaters to determine diet composition. In spring 1997, we found that short-tailed shearwaters were consuming predominately the euphausiid Thysanoessa raschii, a diet expected on the basis of past studies. However, in subsequent years, short-tailed shearwater diets in spring contained increasingly larger proportions of fish, in particular, sandlance (Ammodytes hexapterus), as well as other species of euphausiids (T. inermis in 1999). In summer and fall collections, short-tailed shearwater diets were more varied than in spring, and included both fish (age-0 gadids, 21–35% by weight) and a wider variety of euphausiid species (T. inermis and T. spinifera). In summer and fall, crab zoea (August 1998) and copepods (August 1999) were eaten by shearwaters collected while feeding within the inner front. Diets in 1997–1999 were broader than those found in previous studies of short-tailed shearwaters over the inner shelf and Bristol Bay, which had documented diets composed almost solely of T. raschii. Our data are consistent with the hypothesis that euphausiids were less available to short-tailed shearwaters foraging over the middle and coastal domains of the southeastern Bering Sea in 1997–1999 than has previously been true. Our results are also consistent with hypothesis that the inner front can affect the availability of prey to shearwaters.  相似文献   

Application of a coupled discontinuous–continuous Galerkin finite element shallow water model to coastal ocean dynamics     

Cheryl Ann Blain  T. Christopher Massey 《Ocean Modelling》2005,10(3-4):283-315

A coupled discontinuous–continuous Galerkin (DG–CG) shallow water model is compared to a continuous Galerkin generalized wave-continuity equation (GWCE) based model for the coastal ocean, whereby local mass imbalance typical of GWCE-based solutions is eliminated using the coupled DG–CG approach. Two mass imbalance indicators for the GWCE-based model are presented and analyzed. The indicators motivate discussion on the suitability of using a GWCE-based model versus the locally conservative coupled DG–CG model. Both realistic and idealized test problems for tide, wind, and wave-driven circulation form the basis of the study. For the problems studied, coupled DG–CG solutions retain the robustness of well-documented solutions from GWCE-based models and also capture the dynamics driven by small-scale, highly advective processes which are problematic for GWCE-based models. Issues associated with the coupled DG–CG model are explored, including increased cost due to increased degrees of freedom, the necessary application of slope limiters, as well as the actual coupling process.  相似文献   

Rip current charactersitics and their role in the exchange of water and surf diatoms between the surf zone and nearshore     

M. M. B. Talbot  G. C. Bate 《Estuarine, Coastal and Shelf Science》1987,25(6)

Photogrammetric measurements of dye dispersion in a high-energy surf zone provided semi-quantitative measurements of the pattern and flux of water exchange between the surf zone and nearshore. The intensity of current flow, the rip morphology and its position within the surf zone have important ecological implications for the surf zone and nearshore biota. A variety of water-movement patterns was found, ranging from currents which remained confined to the beach terrace to those which involved substantial exchange across the breaker line. In considering rips as exchange mechanisms, two rip types are recognized. Depending on the exchange of water across the breaker line, a rip may be classified as ‘exchange’ or ‘non-exchange’. The ecological significance of these current types is discussed and a classification scheme for rip currents is proposed. Offshore fluxes across the breaker line by rip currents ranged from negligible to 80 m³s⁻¹ rip⁻¹. The estimated maximum flux per running meter of the Sundays River Beach was calculated as 0·0.32m ³ s⁻¹. The half-residence period of surf-zone water ranged from as little as 22 min t0 5 days, averaging 3·6 h.A dichotomy of current patterns found between the water column and surface layers is used to explain the build up of a concentration gradient in cell numbers of the surf diatom Anaulus birostratus within the surf zone despite extensive flushing by surf circulation.  相似文献   

Factors influencing the magnitude of phytoplankton primary production in a high-energy surf zone     

Eileen E. Campbell  G. C. Bate 《Estuarine, Coastal and Shelf Science》1987,24(6)

The main factors influencing phytoplankton primary production in the surf zone of the Sundays River Beach, Algoa Bay have been characterized. These factors include cell concentration, chlorophyll concentration, irradiance, temperature and salinity. Good relationships have been obtained between cell concentration, chlorophyll concentration and primary production. The P-I curves showed dependence on temperature with a linear regression between temperature and I_k values. Light saturation was shown to occur between 300 and 510 μmol m⁻² s⁻¹ at normal field temperatures. T_max and T_min were found to be 34°C and 0°C, respectively; P_max was 25°C. Salinity had a marked effect on primary production with S_max occurring at 60 ppt and an extrapolated S_min at 0 ppt. P_max was found to occur at 30 ppt.  相似文献   

The Multifunctionality of Country Stores: Insights on Resilience from Rural Vermont          下载免费PDF全文

Cheryl Morse 《Geographical review》2018,108(3):457-475

A multifunctionality analysis of built environments within rural landscapes can deepen understanding of how contemporary rural places function. There is an urgent need for this knowledge as small towns in the United States lose socio‐economic infrastructure resulting from restructuring, demographic change, and the centralization of services. This qualitative and exploratory study of country stores in rural Vermont finds that stores operate as key socio‐spatial nodes within broader geographic networks. Analysis of the goods, functions, and services stores furnish reveals the reflexive relationships stores have with the physical and cultural geographies of their regions. In moments of community crisis and under certain conditions, stores exhibit hyper‐functionality. Built environments and their socio‐spatial roles in multifunctional landscapes should be included in analyses of rural community resilience.  相似文献   

Happy to Be Home: Place-Based Attachments,Family Ties,and Mobility among Rural Stayers     

Cheryl E. Morse  Jill Mudgett 《The Professional geographer》2018,70(2):261-269

Migration research has traditionally centered on tracing movement; however, the experience of staying in place has begun to capture scholarly attention. Drawing on data from an online residential decision-making survey, this article focuses specifically on the reasons that contented Vermonters cite for remaining in their home state. A statistical analysis of responses reveals the dominance of place-based factors and family ties in stayers' residential decision making. Contented stayers highly value landscape and community, as well as living near family. Biographical sketches of individual respondents show the emotional dimensions of choosing to stay, as well as the diverse forms of mobility that contented stayers exercise to remain happy at home. In its focus on stayers, this research situates itself within new geographic inquiries into place attachment and studies of “immobile” populations.  相似文献   

Aeolian sediment flux decay: Non-linear behaviour on developing deflation lag surfaces     

Cheryl Mckenna Neuman  W. G. Nickling 《地球表面变化过程与地形》1995,20(5):423-435

Wind tunnel simulations of the effect of non-erodible roughness elements on sediment transport show that the flux ratio q/q_s, shear velocity U*, and roughness density λ are co-dependent variables. Initially, the sediment flux is enhanced by kinetic energy retention in relatively elastic collisions that occur at the roughness element surfaces, but at the same time, the rising surface coverage of the immobile elements reduces the probability of grain ejection. A zone of strong shearing stress develops within 0·03 to 0·04 m of the rough bed because of a relative straightening of velocity profiles which are normally convex with saltation drag. This positive influence on fluid entrainment is opposed by declining shear stress partitioned to the sand bed. Similarly, because the free stream velocity U_f is fixed while U_* increases, velocity at height z and particle momentum gain from the airstream decline, leading eventually to lower numbers of particles ejected on average at each impact. When the ratio of the element basal area to frontal area σ is approximately equal to 3·5, secondary flow effects appear to become significant, so that the dimensionless aerodynamic roughness parameter Z₀/h and shear stress on the exposed sand bed T_s decrease. It is at this point that grain supply to the airstream and saltation drag appear to be significantly reduced, thereby intensifying the reduction in U_*. The zone of strong fluid shear near the bed dissipates.  相似文献   

Inhibition of phytoplankton photosynthesis by the WSF of used lubricating oil     

G.C. Bate  Stephanie D. Crafford 《Marine pollution bulletin》1985,16(10):401-404

The photosynthetic rates of five phytoplankton species were inhibited following treatment with the water-soluble fractions (WSF) of used lubricating oil. Exhaust oil from an outboard motor inhibited photosynthesis in three out of the five species tested which indicates a species specific response in the case of this form of oil pollution. Water-soluble fractions from Qatar crude had no inhibitory effect on any of the species tested but had a stimulatory effect on the photosynthetic rate of one species. Both oxygen evolution and carbon assimilation were inhibited by the water-soluble fraction of used lubricating oil. In four out of five species, used lubricating oil WSF caused a net oxygen consumption during the light phase rather than a net oxygen release. These data indicate that used lubricating oil water-soluble fractions are especially toxic to phytoplankton.  相似文献