Effects Of Water Level Changes Research Articles

댐 건설 기간 수위변화가 하반림 일대 습지 식생에 미치는 영향 -한탄강댐을 사례로-

This study was performed to monitor the effects of water level change on changes of landscape, vegetation community, and species diversity of riparian forest. Hantan river dam, study area, has been constructed in the area of Chansoo-myeon, Pocheon-si and Yeoncheon-eup, Yeoncheon-gun, Gyeonggi-do, which is a dam for flood control only in flooding season. Landscape changes were notable after the construction of coffer dam, and the changes were caused by water level increase in areas of riparian forests which consisted of mainly withered willow as a dominant species in the flooding season. It changed vegetation communities of riparian forest from Phragmites japonica and Salix koreensis to Phragmites japonica. Species diversity index was lowest in 2010 when the coffer dam was constructed and showed an increasing trend later. Thus, this study is well in agreement with a previous report that plants of the genus Salix wither by muddy water during flooding and also suggests, controlling water level of river and prediction of water level change's effects should be considered when any facilities are planned.

An Optode Sensor Array for Long-Term In Situ Oxygen Measurements in Soil and Sediment

Long-term measurements of molecular oxygen (O) dynamics in wetlands are highly relevant for understanding the effects of water level changes on net greenhouse gas budgets in these ecosystems. However, such measurements have been limited due to a lack of suitable measuring equipment. We constructed an O optode sensor array for long-term in situ measurements in soil and sediment. The new device consists of a 1.3-m-long, cylindrical, spear-shaped rod equipped with 10 sensor spots along the shaft. Each spot contains a thermocouple fixed with a robust fiberoptic O optode made by immobilizing a layer of Pt(II) meso-tetra(pentafluorophenyl)porphine in polystyrene at the end of a 2-mm polymethyl methacrylate plastic fiber. Temperature and O optode readings are collected continuously by a data logger and a multichannel fiberoptic O meter. The construction and measuring characteristics of the sensor array system are presented along with a novel approach for temperature compensation of O optodes. During in situ application over several months in a peat bog, we used the new device to document pronounced variations in O distribution after marked shifts in water level. The measurements showed anoxic conditions below the water level but also diel variations in O concentrations in the upper layer presumably due to rhizospheric oxidation by the main vegetation The new field instrument thus enables new and more detailed insights to the in situ O dynamics in wetlands.

Valuing water level changes in reservoirs using two stated preference approaches: An exploration of validity

The combination of travel cost (TCM) and contingent behaviour (CB) methods is a relatively new research avenue in the recreational valuation community. Contrary to simple TCM applications, TCM–CB facilitates the ex ante valuation of marginal welfare effects resulting from environmental quality or quantity changes, similar to the contingent valuation method (CV). Even though TCM–CB is highly policy relevant, i.e. to inform changes in management regimes at recreational sites, the validity of estimates has hardly received any attention and little is known about the performance of TCM–CB compared to CV. In this paper, TCM–CB and CV are explored with respect to several validity tests in a case study on the recreational effects of water level changes in a reservoir. Overall, the findings reveal that TCM–CB and CV perform equally well in terms of theoretical validity, but that the marginal recreational value varies significantly between the two methods. We also observe that both methods face similar internal difficulties with respect to the stability of values when the order of a set of valuation questions is changed.

Effects of water-level change on morphometric production indicators in two meromictic lakes

Effects of water-level change on morphometric production indicators in two meromictic lakes

Water level as the mediator between climate change and phytoplankton composition in a large shallow temperate lake

We studied the effect of water level changes in Lake Vortsjarv (270 km2, mean depth 2.8 m) on the abundance and composition of phytoplankton based on a 35-year database. Analysis of long time-series (since 1884) revealed a strong influence of the North Atlantic Oscillation on the water level in this lake. The registered maximum range of water level in L. Vortsjarv is 3.2 m, which corresponds to 1.4 times difference in the lake area, 2.5 times difference in the mean depth and 3.5 times difference in volume. Cyanobacteria build up 2/3 of the average phytoplankton biomass during the ice-free period (May–October). On average 75% of the cyanophyte biomass is formed by four filamentous species. Centric diatoms from the genera Aulacoseira and Cyclotella dominate in the biomass of diatoms. Phytoplankton biomass was significantly lower in years of high water level and the changes were unrelated to nutrient loading. The share of filamentous blue-greens among phytoplankton followed the changes in the water level while there was a succession of dominants. Planktolyngbya limnetica reached its maximum in the low water period in the middle of the 1970s. Limnothrix redekei and L. planktonica started to dominate in the high water period in the 1980s while the total biomass decreased substantially in spite of high nutrient loading. During the low water period in the 1990s, the role of the nitrogen-fixing species Aphanizomenon skujae increased. The succession was caused by changes in light and nutrient availability in the fully mixed environment. As low light species, filamentous Limnothrix spp. were most successful in competition for light and phosphorus in deeper water while A. skujae was favoured by high light intensities and a low N/P ratio in shallow water.

Risk Assessment of some Revetments in Southwest Wales, United Kingdom

The new risk assessment model in which the second-order reliability method and the importance sampling Monte Carlo (ISMC) simulations were interrelated was implemented to Wiseman’s Bridge, Newport, and Broadhaven revetments in the Pembrokeshire Coast National Park, southwest Wales, United Kingdom. The tidal range of the site and the storm surge were randomly generated at the first stage of ISMC simulation from the probability distributions describing the phenomena. At the second stage, the damage probability was predicted by approximating the limit-state surface by a quadratic one having the identical curvature at the design point. Newport and Broadhaven revetments were safe, but the revetment at Wiseman’s Bridge needed strong maintenance. The risk assessment model reflected the effect of water level changes (circa 6 m above ordnance datum) on the reliability of rubble mound revetments by simulating the environmental conditions at the sites. As the uncertainties inherent in design parameters were extensiv...

Effects of water level changes and wading bird abundance on the foraging behaviour of blacknecked storksEphippiorhynchus asiaticus in Dudwa National Park, India

The effect of water level changes and wading birds' abundance on the foraging behaviour of the blacknecked stork (BNS) Ephippiorhynchus asiaticus was studied from January 1995 to June 1997 in Dudwa National Park, Uttar Pradesh. Our observations indicate that BNS territoriality increased as food levels became depleted, resulting in increased rates of aggression towards intruders. Chasing or aggression was more intense during the early period (February and March) than the late period (April, May and June). Most of (> 50%) the aggressive encounters were observed between 0600 and 1000 h of the day. Seventeen species (including BNS) were observed interacting with BNS, throughout the study period. Most interactions were with the spoonbill, Platalea leucorodia (67.4%), followed by the whitenecked stork, Ciconia episcopus (16.6%). The distance (while foraging) between BNS and other wading birds varied significantly (P < 0.001) between years indicating that BNS and other water birds foraged at different water depths and thereby explored the wetlands fully. Spoonbills were chased often; the number varied from 1 to 43 birds. BNS occasionally accepted the presence of other wading birds, including spoonbills and started foraging amidst them. This led to successful foraging of BNS (solitary feeder). Other fish-eating bird species and their numbers also limited the food consumption of foraging BNS as they had to spend time chasing away the intruders. Availability of the preferred prey fish species, Heteropnestus fossilis, forced BNS to stay throughout the year in their respective territories. High (> 60 cm) water levels were not suitable for BNS even though the patch had high prey abundance.

The different primary producers in a small African tropical reservoir during a drought: temporal changes and interactions

1. The biomass of the different primary producers, and their relative contributions to the total, were measured quarterly from July 1997 to September 1998 in a tropical reservoir (Brobo, Côte‐d'Ivoire). The study period was marked by an exceptional decrease in the water level as a result of a long drought with only one significant rainfall in June 1998. 2. In July 1997, at the beginning of the usual rainy season, the level of the lake was normal and the ecosystem was in a moderately clear water state dominated by littoral macrophytes, mostly Potamogeton octandrus (more than 55% of the 6.4 tons of carbon of the total primary biomass). The microphytobenthos (19%) and the phytoplankton (25%) were secondary contributors, whereas the periphyton on macrophytes (0.5%) and the epixylon (periphyton on dead flooded trees, 0.3%) were negligible. 3. As a result of the steady decline in water level due to a lack of rain, the macrophytes were progressively stranded on the shores and had disappeared by March 1998. From this time, microalgae (microphytobenthos and phytoplankton) became dominant. Their combined biomass increased slowly from 2.8 tons of carbon in July 1997 to 3.7 tons in September 1998. The microphytobenthic biomass contributed 78% to the total in March, 55% in June and 60% in September, while other contributions were mainly due to the phytoplankton. The epixylon remained negligible throughout the study (≤0.5% of the whole primary biomass). 4. The distribution and temporal changes in the biomass during each survey were mainly linked to hydrology and to interactions between primary producers. 5. The effect of water level changes on free (planktonic) and fixed primary producers (periphytic microalgae and rooted macrophytes) is discussed.

Effects of water-level changes induced by weirs on the distribution of littoral plants along the River Murray, South Australia

In 1988 a survey was made of the River Murray between Locks 2 and 4 (153 river-km) to determine whether the distributions and relative abundances of littoral plants are influenced by water-level variations associated with weir operations. Of 20 recorded plant species, some, including Cyperus sp, and Myriophyllum verrucosue, occurred in regions downstream of each weir and hence were exposed to maximal variation in river levels. Others, notably Typha spp., favoured the regions above each weir, where levels are comparatively stable. The influences of physical channel characteristics such as bank slope, bank erosion and sediment composition and of other environmental factors were not clear. These effects may have been obscured by differences in the natures of the two pools and by a tendency for factors correlated with the water-level gradients to be 'reset' at each weir. Changes in the flow behaviour of the river since 1990 suggest that these survey data may later prove useful in evaluating the effects of high turbidities associated with regulated flows from the Darling River.

Statistical evaluation of hydrologic conditions in the vicinity of abandoned underground coal mines around Cannelburg, Indiana

A statistical analysis of daily water-level changes in an abandoned coal mine indicates that precipitation affects the potentiometric level of the mine, independent of associated atmospheric pressure changes and changes in the water level of an overlying aquifer. The independent statistical effect of precipitation (0.99 cm of water-level change per centimeter of rainfall) is interpreted to reflect either lateral percolation from the coalbed's subcrop (1.2 km from the mine) or rapid recharge through mine-associated pathways, such as poorly plugged shafts, boreholes, or subsidence fractures. The relationship between water-level changes in the mine's voids and changes in the overlying aquifer is also statistically significant, but the regression coefficient (0.04) is an order of magnitude smaller than that for precipitation, indicating that vertical percolation (which is represented by covariance of the two aquifers) through undisturbed overburden may be less effective than the recharge associated with precipitation that bypasses the overburden. An equivalent analysis of water-level changes in an underlying unmined coalbed indicated that precipitation had a weaker direct effect (regression coefficient of 0.34, compared with 0.99), although it was still the dominant independent variable. In contrast, the effect of water-level changes in an overlying aquifer (the flooded mine itself) was relatively stronger (regression coefficient of 0.15, compared with 0.04), indicating that vertical percolation through interburden is more important at depth.

Cooling as Reinforcing Stimulus inAplysia

An experiment was carried out to investigate the role of temperature in the previously reported reinforcing effect of an increase in sea water level in Aplysia . In the present experiment, it was found that the reinforcing effect of water level change on rod-pressing behavior in Aplysia depends on a decrease in temperature associated with water level change. In order study modification of rod pressing behavior produced by contingent increase in water level and decrease in temperature, the rate and latency of rod-press responses in experimental animals where compared with those of yoked control animals exposed to non-contingent water level and temperature change. Higher response rates and shorter response latencies were obtained from experimental over yoked control animals but only the shorter latencies of experimental animals were attributed to a behavioral change resulting from contingent water level and temperature reinforcement.