Hydrological setting

In this section a comparison is presented between the PNEC of LAS for the various environmental compartments, based on the calculations in the comprehensive risk assessment study conducted by HERA (Human and Environmental Risk Assessment on ingredients of European household cleaning products) [16], and the concentrations of LAS measured at different locations covering a broad range of distinct site characteristics (hydrological settings, discharge situation, climatic conditions). 

The cost of an SVE system varies with the size of the site, nature of the contaminants, and hydrological setting. Cost estimates for in situ SVE range from 10 to 50 per cubic meter of soil or from 10 to 40 per cubic yard (USEPA, 1989). 

In the case of a hazardous waste disposal site, the geo-hydrologic setting characteristics must now be carefully considered to assess the existence of subsurface exposure routes. Also, the potential for exposure from air emissions and surface runoff must be quantified where possible. Overall, the significant factors would include (1) evaluating the volatility of the wastes which could lead to short- and long-term exposure to air... 

LaBaugh J. W. (1988) Relation of hydrologic setting to chemical characteristics of selected lakes and wetlands within a climate gradient in the North-Central United States. Verh. Int. Ver. limnol. 23, 131 — 137. 

Warren, J.K. (1982) Hydrologic setting, occurrence, and significance of gypsum in late Quaternary salt lakes, South Australia. Sedimentology 29, 609-637. 

Some models require calibration to optimize input parameters they are best used in a research setting where it is possible to make measurements with which to calibrate the model for a particular site. Appropriate measured hydrologic data are seldom available to calibrate a model for a particular landfill site. Therefore, engineering models used for ET cover design should not require calibration. 

The user specifies which set of sections will be executed in a given run. For example, he may initially "switch on" only SNOW and PWATER, to calibrate the simulated hydrological behavior of a land-segment to observed data. Then he may turn on MSTLAY and... 

Split-sample" field testing Involving calibration and verification on separate data sets, often for different time periods at one site. This approach has been used widely in hydrologic modeling and has general utility for model testing. 

As we have indicated in the previous sections, there is little information on sediment transport in the River Ebro, and most of it is concentrated in the lower reaches of the catchment, downstream the reservoir complex of Mequinenza-Riba-roja-Flix (Fig. 1). We present here a summary of the results obtained from direct measurements on suspended and bedload obtained by the UdL group during the period 2002-2004 upstream (i.e. SMS) and downstream (i.e. MEMS) the reservoir complex, together with the data collected downstream from the dams during the period 2005-2008 (in the later case referred only to suspended sediment). A hydrological context is provided for each of the sediment transport data sets. 

A relatively simple statistical downscaling technique which may be applied quickly to a large number of models is the use of correction factors based on monthly relationships between observed data collected at a particular weather station and the relevant RCM control data set for the appropriate grid-cell [40], These monthly differences (for temperature) and ratios (for precipitation) between the control and the point observations (i.e. not the gridded interpolated CRU data set) can then be used to correct the daily RCM control and scenario data. This gives bias-corrected scenarios of temperature and precipitation, which can then be used as input to hydrological models for the exploration of various management and policy formulations. 

---