Seasonal change in heat flux at the water-bottom sediment boundary in a small lake

Heat exchange with bottom sediments is the main component of the thermal regime of ice-covered shallow lakes of the temperate zone, which explains the importance of its study and parameterization for inclusion in numerical models. Circulations arising in ice-covered lakes due to heat exchange with bottom sediments, and existing for several months, can make a significant contribution to the transport of dissolved and suspended particles along the water column. The aim of this work was to study the seasonal variability of the heat flux at the waterbottom boundary in a shallow lake during the under-ice period, including the period of spring under-ice convection. Based on the analysis of data from high-frequency (minute) long-term measurements of water temperature in the bottom area of a small lake in the temperate zone, a wide range of variability of the heat flux across the water-bottom boundary during the winter from minute to daily fluctuations was established. The role of the spring under-ice heating in the change in the heat flow at the water-bottom boundary is shown. It is shown that shallow areas of the lake bottom, falling into the zone of influence of spring subglacial convection, can accumulate heat already at the end of the ice period. The comparison of temperature fluctuations in the deep-water part of the lake and tin he area with depths close to the average is carried out. It is shown that the spectrum of temperature fluctuations has similar periods, however, in time, sharp temperature jumps in different areas of the lake do not coincide.

Club Formation and Response To Natural Disaster: An Example From South Carolina

In 2016, Hurricane Matthew caused approximately 10 billion dollars of damage in the United States and nearly 350 million dollars in South Carolina. The historic rainfall damaged or completely destroyed roads, bridges, buildings, crops, and dams. This paper documents how one small lakefront community in eastern South Carolina formed a de facto Buchanan Club to fund the reconstruction of a dam destroyed by Matthew and restore a small lake, an exemplary club good. This private response was needed because both the Federal and State governments declined public assistance. In the end and roughly approximately two years after Matthew, the dam was repaired and the lake refilled with the rainfall of Hurricane Florence.

Simulated range of mid-Holocene precipitation changes to extended lakes and wetlands over North Africa

Enhanced summer insolation over North Africa induced a monsoon precipitation increase during the mid-Holocene, about 6000 years ago, and led to a widespread expansion of lakes and wetlands in the present-day Sahara. This expansion of lakes and wetlands is documented in paleoenvironmental sediment records, but the spatially sparse and often discontinuous sediment records provide only a fragmentary picture. Former simulation studies prescribed either a small lake and wetland extent from reconstructions or focused on documented mega-lakes only to investigate their effect on the mid-Holocene climate. In contrast to these studies, we investigate the possible range of mid-Holocene precipitation changes in response to a small lake extent and a potential maximum lake and wetland extent. Results show that the maximum lake and wetland extent shift the North African rain belt about 3 ° farther northward than the small lake extent. Vegetated wetlands cause a larger precipitation increase than the equally-large lakes due to their high surface roughness. A moisture budget analysis reveals that both, lakes and wetlands, cause an enhanced inland moisture transport and local moisture recycling to their southern side. In contrast, increased moisture advection by the Harmattan winds causes a drying response to the north of the lakes and wetlands. These results indicate that the latitudinal position of the lakes and wetlands influences the northward extension of the African summer monsoon. In the sensitivity experiments, the northern position of West Saharan lakes and wetlands substantially contributes to the strong monsoon northward shift seen in the maximum lake and wetland simulations.

Diagnostic Simulation of Water Age in Small Lake of Bosten Lake

Concerns have increased regarding water quality deterioration in arid land water. Water age is a useful indicator of the susceptibility of water bodies to water quality deterioration and is helpful for knowing the basic mechanisms governing the transport of materials through water bodies. In the current study, the spatial distributions of water age in the small lake of Bosten Lake (hereinafter referred to as small lake) were investigated with a two-dimensional hydrodynamic model built on the basis of the Environmental Fluid Dynamics Code (EFDC) model. In particular, the influences of different water flow periods, farmland drainages, and wind directions on water age distributions in the small lake were investigated. The modeled water age in the small lake has high spatial variability. The water age is maximum at the northeastern part and minimum at the center of the small lake. The water age in the small lake is lower during wet periods and gets larger for dry periods. After five years’ simulation, the average water age in the whole small lake system was 594, 684, and 794 days under wet, normal, and dry periods. Increasing the hydraulic connectivity of the small lake can reduce its water age by opening its ecological gate inflow and Ahongkou gate outflow. This is the more favorable hydraulic conditions promoting water exchange in most regions of the small lake and can be used in hydraulic engineering to improve its water age. The farmland drainages should be controlled around the small lake. The mean water age of the whole small lake under the northwestern wind is lower than that under the southwestern wind. The simulated results provide important information for comprehending the water exchange efficiency, help in discovery of areas of the small lake most likely to experience water quality degradation, and can be used to design the engineering projects to improve or protect the water environment.