共查询到4条相似文献,搜索用时 0 毫秒
1.
One predicted impact of the construction of the hydroelectric plant of Brégnier-Cordon (Upper Rhône River, France) was the rise of the water table in the part of the plain situated upstream from the power plant. This impact made it possible to test the hypothesis that the slowing, indeed the halting, of ecological successions occurs in the former channels upstream from the power plant because of the increase of seepage supply through coarse alluvium. The vegetation of two braided former channels, one situated upstream (impacted site) and one downstream (reference site) of the power plant was studied over a period of nine years, before (1981) and after (1985, 1986, 1987, and 1989) the construction of the hydroelectric power-plant. The two sites had similar vegetation and successional stages at the beginning of the study. The seepage supply increases in the impacted site resulted in the establishment ofChara globularis andRiccia fluitans, indicating groundwater influence, but, after halting in 1985–1986, the ecological succession proceeded slowly again in 1987 and 1989, depicted by continuing eutrophication (expressed particularly by the increasing abundance ofCeratophyllum demersum). As expected, ecological succession was not halted in the reference site. Terrestrialization processes were apparent and changes were more rapid at its upstream part. 相似文献
2.
3.
Resolution and Analysis of Spatial Variations and Patterns in an Urban Lake with Rapid Profiling Instrumentation 下载免费PDF全文
Anthony R. Prestigiacomo Steven W. Effler David A. Matthews 《Journal of the American Water Resources Association》2015,51(1):200-213
Rapid response vertical profiling instrumentation was used to document spatial variability and patterns in a small urban lake, Onondaga Lake, associated with multiple drivers. Paired profiles of temperature, specific conductance (SC), turbidity (Tn), fluorometric chlorophyll a (Chlf), and nitrate nitrogen (NO3?) were collected at >30 fixed locations (a “gridding”) weekly, over the spring to fall interval of several years. These gridding data are analyzed (1) to characterize phytoplankton (Chlf) patchiness in the lake's upper waters, (2) to establish the representativeness of a single long‐term site for monitoring lake‐wide conditions, and (3) to resolve spatial patterns of multiple tracers imparted by buoyancy effects of inflows. Multiple buoyancy signatures were resolved, including overflows from less dense inflows, and interflows to metalimnetic depths and underflows to the bottom from the plunging of more dense inputs. Three different metrics had utility as tracers in depicting the buoyancy signatures as follows: (1) SC, for salinity‐enriched tributaries and the more dilute river that receives the lake's outflow, (2) Tn, for the tributaries during runoff events, and (3) NO3?, for the effluent of a domestic waste treatment facility and from the addition of NO3? solution to control methyl mercury. The plunging inflow phenomenon, which frequently prevailed, has important management implications. 相似文献
4.
Kyosuke Onishi Tetsuyuki Ueyama Toshifumi Matsuoka Dai Nobuoka Hideki Saito Hiroyuki Azuma Ziqiu Xue 《International Journal of Greenhouse Gas Control》2009,3(3):311-321
A pilot-scale experiment for carbon dioxide (CO2) sequestration was undertaken at the Nagaoka test field in Japan. Time-lapse crosswell seismic tomography was conducted to detect and monitor the movement of CO2 injected into an aquifer. We applied difference analysis with data normalization (DADN) to the time-lapse data to eliminate false images that were apparent in a conventionally processed difference section. Conventional difference analysis calculates travel-time delays after inversion, whereas the DADN method calculates them from raw travel-time records before inversion. Thus, fewer errors are generated with the DADN method compared to a conventional inversion analysis. We applied the DADN method to time-lapse tomography data recorded before and after the injection of CO2 and computed the velocity variation in a subsurface section, which clearly showed the distribution of CO2 flooding within a high permeability zone in the aquifer and showed no CO2 leakage into the caprock. Our results also show the maximum velocity decrease as a result of CO2 injection was about 9%, which is close to the results obtained in laboratory experiments. Finally, numerical simulations were inverted to test the effectiveness of the conventional and DADN methods in dealing with noise. These tests showed that the DADN method effectively reduces unique coherent noise for particular receiver and source combinations. We concluded that the DADN method provides useful data for monitoring the flow of CO2 sequestered in underground aquifers. 相似文献