Surface Water Supply Index Research Articles

SWSI 가뭄지수를 보완한 준분포형 수문학적 가뭄평가 연구

A hydrological drought index, MSWSI (Modified Surface Water Supply Index) was suggested based on SWSI. South Korea was divided into 32 regions considering the distribution of available gauge station of precipitation, dam storage, stream water level and natural groundwater level. The indices estimated in the regions represent a spatially distribution of drought. Monthly MSWSI was evaluated for the period of 1974 and 2001. The result was compared with PDSI and checked the applicability of the suggested index in our hydrologic drought situation.

SWSI를 이용한 준분포형 수문학적 가뭄 평가

A hydrological drought index, MSWSI (Modified Surface Water Supply Index) was suggested based on SWSI (Surface Water Supply Index). With the available data of spatially distributed observation station of precipitation, dam storage, stream water level and natural groundwater level, South Korea was divided into 32 regions. This was conducted to represent the calculated index as a spatially distributed information. Monthly MSWSI was evaluated for the period of 1974 and 2001. It is necessary to compare this result with PDSI (Palmer Drought Severity Index) and SPI (Standard Precipitation Index), and check the applicability of the suggested index in our hydrological drought situation.

가뭄평가를 위한 가뭄지수의 비교 연구

본 연구에서는 자연재해의 하나인 가뭄을 정량적인 방법으로 해석하기 위하여 가뭄에 영향을 미칠 수 있는 각 수문인자를 수치화하고, 이를 이용하여 증발산과 누가강수량의 편차를 산정해서 가뭄을 정량화하는 PDSI와 유역 단위의 지수를 산정하는 SWSI 및 다양한 지속기간별 지수를 산정하는 SPI를 이용해서 대상 유역인 낙동강 유역의 가뭄지수를 산정 및 비교하였으며, 가뭄대책에 대한 기본 정보를 제공하고자 하였다. 이를 통해, PDSI의 경우 지속되는 가뭄기간동안의 변화를 살피는데 유리하고, SWSI는 가뭄이 시작되는 몇 개월에 해당하는 가뭄을 판단하거나 단기간 수문인자의 변동을 통한 가뭄을 판단하는데 이용될 수 있으며, SPI는 그 지속기간이 짧은 경우 단기간의 가뭄을, 지속기간이 길어지면 장기간의 가뭄을 나타내는데 유리할 것으로 분석되었다. 또한, SWSI와 PDSI 및 SPI를 이용하여 과거 가뭄을 살펴본 결과 '94<TEX>${\sim}$</TEX>'97년간 지속된 가뭄이 과거 가뭄사상 중 가장 극심하며 긴 가뭄기간을 지닌 것으로 판단되었으며, SWSI를 통해 기존에 파악되지 못했던 수문학적 가뭄이 1992년에 발생했었음을 알 수 있었다. 이상의 분석을 통하여 볼 때 SWSI와 PDSI 및 SPI는 가뭄을 정량적으로 나타내는데 아주 유효한 방법이며, 각각의 지수가 가지는 장 단점에 따라 가뭄을 파악할 경우 효과적일 것으로 판단되었다. In order to quantitatively identify historical drought conditions and to evaluate their variability, drought indices commonly used. The calculation method for the drought index based on the principal hydrological factors, such as precipitation and reservoir storage, can estimate the duration and intensity of a drought. In this study the Palmer-type formula for drought index is derived for the Nakdong River basin by analyzing the monthly rainfall and meteorological data at 21 stations. The Palmer Drought Severity Index(PDSI) is used for dry land sectors to evaluate the meteorological anomaly in terms of an index which permits time and space comparisons of drought severity. The Surface Water Supply Index(SWSI) is devised for the use in conjunction with the Palmer index to provide an objective indicator of water supply conditions in Nakdong River basin. The SWSI was designed to quantify surface water supply capability of a watershed which depends on river and reservoir water The Standardized Precipitation Index(SPI) is evaluated for various time periods of 1 to 12 months in Nakdong River basin. For the purpose of comparison between drought indices correlation coefficient was calculated between indices and appropriate SPI time period was selected as 10 months for Nakdong River basin. A comparative study is made to evaluate the relative severity of the significant droughts occurred in Nakdong River basin since 1976. It turned out that <TEX>$'94{\sim}'97$</TEX> drought was the worst drought in it's severity. It is found that drought indices are very useful tools in quantitatively evaluating the severity of a drought over a river basin.

A Review of Twentieth-Century Drought Indices Used in the United States

The monitoring and analysis of drought have long suffered from the lack of an adequate definition of the phenomenon. As a result, drought indices have slowly evolved during the last two centuries from simplistic approaches based on some measure of rainfall deficiency, to more complex problem-specific models. Indices developed in the late nineteenth and early twentieth century included such measures as percent of normal precipitation over some interval, consecutive days with rain below a given threshold, formulae involving a combination of temperature and precipitation, and models factoring in precipitation deficits over consecutive days. The incorporation of evapotranspiration as a measure of water demand by Thornthwaite led to the landmark development in 1965 by Palmer of a water budget-based drought index that is still widely used. Drought indices developed since the 1960s include the Surface Water Supply Index, which supplements the Palmer Index by integrating snowpack, reservoir storage, streamflow, a...

Revised Surface‐Water Supply Index for Western United States

The surface‐water‐supply index (SWSI) was introduced in Colorado in the early 1980s as a better indicator of water availability in the western United States than is the Palmer drought index. Similar indexes have been subsequently developed in Oregon and Montana. These indexes have found great usefulness in drought monitoring and in triggering specific drought‐related activities by state governments. Two conceptual weaknesses exist in the current SWSIs: (1) Subjective assignment of values to coefficients; and (2) obscured statistical properties of the index. Revisions to overcome these weaknesses include a specific definition of surface‐water‐supply, use of streamflow volume forecasts, and appropriate handling of data to achieve the desired statistical properties of the index. It is also suggested that indexes for individual hydrologic components be developed to provide supporting information to the SWSI. An example of the development of the revised SWSI is given for the Flathead River basin in Montana.