Semi-automatic reduction and upscaling of large models: A farm management example

Research questions at the regional, national and global scales frequently require the upscaling of existing models. At large scales, simple model aggregation may have a prohibitive computational cost and lead to over-detailed problem representation. Methods that guide model simplification and revision have the potential to support the choice of the appropriate level of detail or heterogeneity within upscaled models. Efficient upscaling will retain only the heterogeneity that contributes to accurate aggregated results. This approach to model revision is challenging, because automatic generation of alternative models is difficult and the set of possible revised models is very large. In the case where simplification alone is considered, there are at least n²−1 possible simplified models where n is the number of model variables. Even with the availability of High Performance Computing, it is not possible to evaluate every possible simplified model if the number of model variables is greater than roughly 35. To address these issues, we propose a method that extends an existing procedure for simplifying and aggregating mechanistic models based on replacing model variables with constants. The method generates simplified models by selectively aggregating existing model variables, retaining existing model structure while reducing the size of the set of possible models and ordering them into a search tree. The tree is then searched selectively. We illustrate the method using a catchment scale optimization model with c. 50,000 variables (Farm-adapt) in the context of adaptation to climatic change. The method was successful in identifying redundant model variables and an adequate model 10% smaller than the original model. We discuss how the procedure can be extended to other large models and compare the method to those proposed by others. We conclude by urging model developers to regard their models as a starting point and to consider the need for alternative models during model development.     

PLANNING FOR DROUGHT: THE ROLE OF STATE GOVERNMENT1

ABSTRACT: Although droughts are a frequent occurrence over much of the United States, response by state and federal government has been ineffective and poorly coordinated. Recently, several states have recognized the value of drought emergency planning and have developed plans to assist them in responding more effectively to prolonged periods of water shortage. These states have created an organizational structure to coordinate the assessment and response activities of state and federal agencies. Each state's drought response plan is unique since each state's water supply and management problems, and their consequent impacts, are unique. The drought response plans developed by Colorado, South Dakota and New York are reviewed here in detail. We recommend that other states affected by frequent and severe water shortages also develop drought emergency plans. These plans will enhance state government's ability to implement effective measures in a timely manner and, ultimately, may provide added incentive for the federal government to develop the national drought response plan called for by the General Accounting Office in 1979.     

Stormflow hydrochemistry of a river draining an abandoned metal mine: the Afon Twymyn, central Wales

Contaminated drainage from metal mines is a serious water-quality problem facing nations that exploit metal mineral resources. Measurements of river hydrochemistry during baseflow are common at mine sites, whilst detailed hydrochemical information regarding stormflow is limited and often confined to a single event. This study investigates the seasonal evolution of stormflow hydrochemistry at an abandoned metal mine in central Wales, UK, and the possible sources and mechanisms of metal release. Significant flushing of metals was observed during stormflow events, resulting in concentrations that severely exceeded water-quality guidelines. The relationship between metal concentrations and river discharge suggests dissolution of efflorescent metal sulphates on the surface of the mine spoil as the principal source of the contamination. High fluxes of Pb during stormflows are linked to extended periods of dry weather prior to storm events that produced water table drawdown and encouraged oxidation of Pb sulphide in the mine spoil. However, some Pb flushing also occurred following wet antecedent conditions. It is suggested that Fe oxide reduction in mine spoil and translatory flows involving metal-rich pore waters results in flushing during wetter periods. Detailed measurements of stormflow hydrochemistry at mine sites are essential for accurate forecasting of long-term trends in metals flux to understand metal sources and mechanisms of release, to assess potential risks to water quality and instream ecology, and to gauge the potential effectiveness of remediation. In order to protect riverine and riparian ecosystems, it is suggested that routine monitoring of stormflows becomes part of catchment management in mining-impacted regions.     

Assessment of the impact of landfill on groundwater quality: A case study of the Pirana site in western India

In present study focus has been given on estimating quality and toxicity of waste with respect to heavy metals and its impact on groundwater quality, using statistical and empirical relationships between different hydrochemical data, so that easy monitoring may be possible which in turn help the sustainable management of landfill site and municipal solid waste. Samples of solid waste, leachate and groundwater were analyzed to evaluate the impact of leachates on groundwater through the comparison of their hydrochemical nature. Results suggest the existence of an empirical relationship between some specific indicator parameters like heavy metals of all three above mentioned sample type. Further, K/Mg ratio also indicates three groundwater samples heavily impacted from leachate contamination. A good number of samples are also showing higher values for and Pb than that of World Health Organization (WHO) drinking water regulation. Predominance of Fe and Zn in both groundwater and solid waste samples may be due to metal plating industries in the area. Factor analysis is used as a tool to explain observed relation between numerous variables in term of simpler relation, which may help to deduce the strength of relation. Positive loading of most of the factors for heavy metal clearly shows landfill impact on ground water quality especially along the hydraulic gradient. Cluster analysis, further substantiates the impact of landfill. Two major groups of samples obtained from cluster analysis suggest that one group comprises samples that are severely under the influence of landfill and contaminated leachates along the groundwater flow direction while other assorted with samples without having such influence.     

Ozone Exposures and Implications for Vegetation in Rural Areas of the Central Appalachian Mountains, U.S.A.

The United States is making the transition from the 1979 1 hr maximum ozone standard to the newly adopted 8 hr ozone standard (3 yr average of the 4th highest maximum 8 hr ozone concentration). Consequently, we analyzed and compared ozone concentrations under both standards from a variety of monitoring sites throughout the central Appalachian region of Kentucky (KY), West Virginia (WV), and Virginia (VA). Data from 1988-1999 were used to determine how ozone exposure between the two metrics compared for remote sites. Most sites exceeded the 1 hr standard in 1988-1990 due to the 3 yr averaging and multiple high ozone concentrations that occurred over the region in 1988. All sites were in compliance with the 1 hr standard every year after 1991. It was much more common for the ozone exposure to exceed the 8 hr standard, particularly from 1997-1999. Many sites showed exceedences beginning in 1995; Big Meadows (VA) exceeded the 8 hr standard all years except 1994 and 1996. Response of vegetation to ozone in these areas was determined using the combination of W126 values (sigmoidally weighted exposure index), the number of hours that average concentrations > or = 0.10 ppm (N100), and the presence of moderate or more extreme droughts. In general, W126 and N100 values suggested that negative vegetation growth responses over most of the 12 yr would have been minimal for most sites, even for those exceeding ozone standards. Drought-induced stomatal closures would have overridden more extreme negative growth responses at all but the Big Meadows site in 1988.     

Landscapes for tomorrow

Seven different landscapes that might realistically represent the Yorkshire Dales National Park in the lifetime of the present generation were created out of detailed interviews with policy managers, landowners and farmers. These landscapes were imaged in the form of water colour paintings, then incorporated with appropriate explanatory commentary into a large graphic display, a video sequence, a floor game and a leaflet. The interpretive material was taken to the public as a touring exhibition, travelling around the National Park over two consecutive summers. The exhibition was designed to be participatory: its purpose to discover how far people could grasp the processes leading to landscape change, become aware of why these forces were happening and become sufficiently concerned for the future to participate in the creation of landscape design of their choice. The results revealed that the approach experimented with was successful in meeting its aims, that those less conversant with the issues were more influenced than those already familiar with some of the causes of change and that participatory interpretation can be a highly educative and enjoyable experience.