Woonsup Choi

Catchment-Scale Hydrological Response to Climate-Land-Use Combined Scenarios: A Case Study for the Kishwaukee River Basin, Illinois

This paper examines how the Kishwaukee River basin located between Chicago and Rockford, Illinois, would respond to various climate-land use combined scenarios. The Hydrological Simulation Program-Fortran was calibrated and repeatedly run with eight climate-land-use combined scenarios generated from a general circulation model (HadCM3) and a dynamic urban growth model. The climate scenarios were based on two IPCC SRES emission scenarios (A2 and B2) and the land-use scenarios were based on four economic growth scenarios. The results of the study indicate that total runoff is predicted to decrease noticeably to moderate climate change but shows little sensitivity to land-use change. What is sensitive to land-use change is surface runoff, which is predicted to change from -9.9% to +29.2% depending on land-use scenarios under the A2 emission scenario. Runoff during summer and the low-flow season is projected to undergo the most severe decrease, up to 41.4% under the B2 emission scenario. Finally, it was found that simply combining climate and land-use scenarios is not enough to show the compounding effect of climate change and land-use change.

Use of the North American Regional Reanalysis for Hydrological Modelling in Manitoba

This study investigates the applicability of temperature and precipitation data from the North American Regional Reanalysis (NARR) for hydrological modelling of selected watersheds in northern Manitoba. For the specific region, it is found that NARR temperature and precipitation data are in much better agreement with observations than a popular global reanalysis data set. The hydrological model SLURP (Semi-distributed Land Use-based Runoff Processes) was set up and calibrated for three catchments (Burntwood, Taylor and Sapochi), using meteorological data from weather stations. When the calibrated models were run with temperature and precipitation data from NARR, runoff was underestimated by approximately 20%. The SLURP model was then recalibrated using the NARR temperature and precipitation data as input. This eliminated much of the bias and provided a goodness-of-fit that was only slightly inferior to simulations with observed weather data. This suggests that SLURP can be adequately calibrated with NARR data and used for modelling hydrological processes in northern Manitoba where weather stations are scarce.

Forest cover changes in North Korea since the 1980s

North Korea used to have abundant forest stocks but underwent substantial deforestation and degradation of forest in recent decades. This study examined morphological changes of forest cover in North Korea between the 1980s and 2000s. Land cover data based on Landsat TM imagery were obtained as images from the Republic of Korea’s Ministry of Environment. The images were processed and used for the morphological spatial pattern analysis (MSPA) and network analysis. MSPA classified the forest cover into morphological classes such as core, islet, bridge, perforation, edge, loop, and branch. The network analysis identified individual networks of forest, each of which represents a patch of connected forest. The results are summarized as follows: (1) forest cover sharply decreased between the 1990s and 2000s, particularly in western provinces; (2) morphological classes indicating forest fragmentation such as islet, branch, and edge consistently increased in their fraction to the total area between the 1980s and 2000s; (3) islet, branch, and edge also increased in number during the same period; (4) forest networks shrank in size and increased in number. Overall, the results demonstrate that deforestation and fragmentation of forest occurred simultaneously in North Korea during the time.

Urbanization and Rainfall–Runoff Relationships in the Milwaukee River Basin

To understand the changing rainfall–runoff relationship, this study examined climate and streamflow data in the Milwaukee River Basin in southeastern Wisconsin, of which four catchments with different degrees of urbanization were selected for analysis. This study analyzed temperature, precipitation, and streamflow data with a range of statistical methods, including the Mann–Kendall test, double-mass technique, and quantile regression. Runoff ratios and extreme flow indexes were higher in more urbanized catchments. Catchments with long-term data (>forty years) showed significantly increasing runoff ratios and slopes in double-mass curves. Overall, there are signs of changes in the rainfall–runoff relationship, but how much they can be attributed to land use changes is uncertain.

Identification of mid-latitudinal regional and urban temperature variabilities based on regional reanalysis data

The objective of the study is to detect geographical and temporal variations of near surface air temperatures over Minnesota and Wisconsin, USA derived from the North American Regional Reanalysis (NARR) dataset. In addition, the study serves to assess the usefulness of NARR temperature data to analyze regional and local temperature variations. Particular emphasis was placed on the analyses on the temperature-modifying effects of the Great Lakes and large urban environments. We analyzed annual mean, daily maximum and minimum, and January minimum and July maximum temperatures for the period 1979–2006 by using methods such as ordinary kriging, principal component analysis, and the Mann–Kendall test. On a regional scale, we found significant effects of the latitude and the Great Lakes on the spatial variability of the data. Furthermore, we found clearly identifiable effects of large urban areas in the study region (Minneapolis—Saint Paul and Milwaukee), which are more evident in the principal component scores than in the temperature data themselves. While we failed to detect significant July maximum temperature trends, we detected significantly increasing trends in January minimum and mean annual temperature datasets in the eastern part of the region. Overall, the present study has demonstrated the potential of using NARR data for urban climate research.

Predicting future urban impervious surface distribution using cellular automata and regression analysis

Urban impervious surfaces are considered as key indicator of urbanization intensity and environmental quality. Due to their significant impact on surface runoff, flood frequency, and water quality, impervious surfaces have been identified as an important indicator for examining the hydrological impact of urbanization. The amount and distribution of impervious surfaces have been estimated using remote sensing and geographic information system (GIS) techniques. Little research, however, has been conducted to predict future impervious surface distributions. To address this problem, we developed an integrated residential/commercial growth and impervious surface distribution model to predict urban impervious surface distribution. Taking Milwaukee River Basin, Wisconsin as a case study, we simulated future residential and commercial developments using a CA model. Further, we developed a linear regression model to predict impervious surface distributions in residential and commercial land uses. Analysis of results suggests that the proposed model performs significantly better than the traditional approaches.

Impacts of climate change and urban growth on the streamflow of the Milwaukee River (Wisconsin, USA)

Hydrological impact studies of climate change increasingly take land use changes into account. However, the Midwestern USA is still understudied in this context. This study investigated the impacts of potential climate change and urban growth on the streamflow characteristics of the Milwaukee River located in southeastern Wisconsin. The Hydrological Simulation Program-Fortran (HSPF) was set up for the catchment and calibrated against observed streamflow data. The calibrated HSPF model was run with a series of climate and urban growth scenarios generated from nine global climate models (GCMs) and a land use simulation model, respectively. The outcomes from the GCMs, statistically downscaled at 10-km grid spacing, generally indicated a warmer and wetter climate by the mid-twenty-first century, and the land use simulation model projected moderate urban growth by the time. Major findings from the study include: (1) land use changes alone resulted in negligible streamflow changes; (2) low flows showed more sensitivity than mean streamflow to climate change; (3) streamflow variability increased with both land use and climate changes, and (4) uncertainty in simulated streamflow among GCMs was larger than uncertainty among the GCM output themselves. The findings suggest that the current pace of urban growth would not pose much threat to the water resources in the area. Considering that low flow indices responded more sensitively than mean streamflow to climate change, measures to improve resilience to drought conditions are recommended. Because land use change impacts were quite small, considering the impact of both climate and land use scenarios did not produce a significantly different result.

Hydrological Impacts of Warmer and Wetter Climate in Troutlake and Sturgeon River Basins in Central Canada

The impact of climate change on water availability in two river basins located in central Canada is investigated. Several statistical downscaling methods are used to generate temperature and precipitation scenarios from the third-generation Canadian Coupled General Circulation Model, forced with different emission scenarios. The hydrological model SLURP is used to simulate runoff. All downscaling methods agree that temperature will increase with time and that precipitation will also increase, although there is considerably more uncertainty in the magnitude of precipitation change. The study concludes that the change in total annual precipitation does not necessarily translate into similar changes in runoff. The seasonal distribution of precipitation changes is important for runoff, as is the increase in evapotranspiration. The choice of downscaling method appears to have a greater impact on runoff projections than the choice of emission scenario. Therefore, it is important to consider several downscaling methods when evaluating the impact of climate change on runoff.

Climate change, urbanisation and hydrological impacts

This paper is a review of recent studies that addressed the hydrological impacts, especially on streamflow, of climate change and/or urbanisation. Articles published between 1996 and 2002 on this subject were reviewed focusing on research methods and results. The main issues addressed with regard to research methods include development of climate change and urbanisation scenarios, assessment of urbanisation, hydrological models, and geographical scale. With regard to the results of studies, combined impact of climate change and urbanisation, linearity of runoff response, and impact on flood were addressed. Overall, there has been significant development in this area, and much of it can be attributed to technological advances. Modelling tools for climate change and urbanisation are becoming more reliable and popular. More studies need to be performed about the combined impact of climate change and urbanisation, and the linearity of runoff response for the theoretical development in this area.

Meteorological and Streamflow Droughts: Characteristics, Trends and Propagation in the Milwaukee River Basin

This study examined meteorological and streamflow droughts for the period from 1951 to 2006 using the Milwaukee River basin in Wisconsin as the study area in an effort to improve the understanding of drought propagation. Specifically, this study aimed to answer the following research questions: (1) What are the temporal trends of meteorological and streamflow droughts identified by drought indicators? (2) How do the drought indicators manifest drought propagation? Meteorological droughts were identified using the Effective Drought Index (EDI), and streamflow droughts were identified using a threshold-level approach. The intensity and duration of both types of drought were found to have decreased over time, most likely due to increasing precipitation. Therefore, in the study area, and likely in the larger region, drought has become of less concern. The propagation of meteorological drought into streamflow drought was detected generally after moderate and severe sequences of negative EDI that eventually led to extreme meteorological drought events. The study finds that both EDI and the threshold-level approach are effective in diagnosing meteorological and streamflow drought events of all durations.