Jaswinder Pal Singh

An evaluation of a commercial CC-NUMA architecture-the CONVEX Exemplar SPP1200

Studies done with academic CC-NUMA machines and simulators indicate a good potential for application performance. Our goal therefore, is to investigate whether the CONVEX Exemplar a commercial distributed shared memory machine, lives up to the expected potential of CC-NUMA machines. If not, we would like to understand what architectural or implementation decisions make it less efficient. On evaluating the delivered performance on the Exemplar we find that, while a moderate-scale Exemplar machine works well for several applications, it does not for some important classes. Further performance was affected by four fundamental characteristics of the machine, all of which are due to basic implementation and design choices made on the Exemplar. These are: the effect of processor clustering together with limited node-to-network bandwidth, the effect of tertiary caches, the limited user control over data placement, the sequential memory consistency model together with a cache-based cache coherence protocol, and lastly, longer remote latencies.

Comparison of Flow and Sediment Modeling Using SWAT and HSPF for Watersheds in the Illinois River Basin

The Illinois State Water Survey has been developing hydrologic and hydraulic models for watersheds in the Illinois River basin as part of the Illinois Rivers Decision Support System (ELRDSS). The hydrologic model is based on the U.S. Environmental Protection Agencys BASINS 3.1 modeling system. The Soil and Water Assessment Tool (SWAT) and Hydrologic Simulation Program — Fortran (HSPF), which are part of the BASINS system, were used to simulate the hydrology of watersheds in the Illinois River basin. Both SWAT and HSPF are comprehensive watershed models that also have the capability to simulate sediment transport. Based on the topographic, and hydrographic, land use, and soil types data, hydrologic models (SWAT and HSPF) were developed for the Court Creek watershed. The Court Creek watershed was divided into 35 subwatersheds and 346 HRUs. Two outlets specified in the models correspond to the streamflow gaging/sediment monitoring stations in the Court Creek watershed. Both models use the same precipitation and temperature data, and the potential evapotranspiration (PEVT), potential surface evaporation (EVAP), and other climate data. The simulation flow and sediments from the HSPF and SWAT models were compared graphically and statistically. Overall relative errors of simulated flow to the observed flow are –0.2 and 3.8% for HSPF and SWAT, respectively, and the relative errors of sediment load are –15 and –47%, respectively. Based on the correlation and the Nash-Sutcliffe Efficiency coefficients of simulated flows, the HSPF model outperformed the SWAT model for daily and monthly flow. However, the models performed almost equally well on the annual average. As for the suspended sediment load, the HSPF model performed slightly better than the SWAT model.

POTENTIAL EFFECTS OF CLIMATE CHANGE AND VARIABILITY ON THE SURFACE WATER RESOURCES OF THE UPPER MIDWEST

Simulated effects of potential climate change on the surface-water resources in the Upper Midwest are compared to the regions historical variability in climate and streamflow, and implications of both climate change and variability on water supply are discussed. Hydrologic models developed for watersheds in Illinois were used to evaluate the response in simulated streamflow to various climate scenarios. The climate scenarios used in the hydrologic simulation are based on outputs from global climate models, and represent a range of potential future climatic conditions. The driest climate scenarios result in a considerable reduction in the simulated flows. The wetter and more moderate climate scenarios generally cause relatively small amounts of change in simulated streamflow amounts, with most estimated streamflow frequency values falling within 15 percent of the simulated record using the 1950–2000 historical climate data. For 5 of the 6 climate scenarios examined in this study, the potential change in average flow is less than 25%. In contrast, there has been considerable historical variability in climatic and hydrologic conditions in the Upper Midwest since the mid-1800s, with variability in the 30-year average precipitation of 10–15 percent and associated changes in average streamflow in excess of 40 percent. Midwestern precipitation and streamflow, in particular, have increased substantially over the last 30 years. It is not known whether the 1971–2000 increase in precipitation and streamflow is a regional manifestation of climate change, or is instead part of the natural variability in the climate. But for now, the recent increasing trends in precipitation may give more credence to the GCM predictions that suggest moderate increases in future precipitation and streamflows.