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

Abstract

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.

为了促进对于乾旱传播的理解, 本研究以威士康辛州密尔沃基河流域作为研究范围, 检视 1951 年至 2006 年间的气象与水文型乾旱。本研究特别旨在回应以下研究问题: (1) 由乾旱指标所指认的气象与水文型乾旱的暂时趋势为何？(2) 乾旱指标如何展现乾旱传播？本研究运用有效乾旱指标 (EDI) 来指认气象型乾旱, 并运用阀值方法来指认水文型乾旱。本研究发现, 两种类型的乾旱强度与时程皆随着时间减少, 并很有可能是由逐渐增加的降雨所导致。因此, 在研究地区、且很有可能在更广泛的区域中, 乾旱已较少受到担忧。本研究在最终导致极端气象乾旱事件的一连串中等与严峻的负面 EDI 之后, 普遍侦测到气象型乾旱传播成为水文型乾旱。本研究发现, EDI 和阀值方法在诊断所有时期的气象与水文型乾旱事件上同样有效。

Este estudio examina las sequías meteorológicas y de flujo de corrientes en el período 1951 a 2006, usando como área de estudio la cuenca del Río Milwaukee, en Wisconsin, dentro del esfuerzo para mejorar el entendimiento de la propagación de la sequía. Específicamente, este estudio se orientó a absolver las siguientes preguntas de investigación: (1) ¿Cuáles son las tendencias temporales en sequía meteorológica y sequía de flujo de corrientes, identificadas por medio de indicadores de sequía? (2) ¿Cómo manifiestan la propagación de la sequía los indicadores de la misma? Las sequías meteorológicas fueron identificadas usando el Índice Efectivo de Sequía (EDI), en tanto que las sequías de flujo de corrientes se identificaron usando un enfoque de nivel de umbral. Se halló que la intensidad y duración de ambos tipos de sequía han disminuido a través del tiempo probablemente debido al incremento de las precipitaciones. En consecuencia, en el área de estudio, y probablemente en la región más extensa, la sequía se ha tornado menos preocupante. La propagación de la sequía meteorológica en forma de sequía de flujo de corrientes se detectó generalmente después de secuencias moderadas y severas del EDI negativo que eventualmente condujeron a eventos de la sequía meteorológica extremos. El estudio descubre que tanto EDI como el enfoque de nivel de umbral son efectivos para diagnosticar eventos de sequías meteorológicas y de flujo de corriente de todas las duraciones.

Key Words:

• drought index
• drought propagation
• hydrological drought
• meteorological drought
• runoff

关键词:

• 乾旱指标, 乾旱传播, 水文乾旱, 气象乾旱, 径流。

Palabras clave:

• índice de sequía, propagación de la sequía, sequía hidrológica, sequía meteorológica, escorrentía

Additional information

Funding

This work was supported by a grant from the International Scholar Program at Kyung Hee University in 2017.

Notes on contributors

Woonsup Choi

WOONSUP CHOI is an Associate Professor in the Department of Geography, University of Wisconsin–Milwaukee, Milwaukee, WI 53201. E-mail: [email protected]. His research interests include hydroclimatology and human impacts on hydrological processes.

Hi-Ryong Byun

HI-RYONG BYUN is an Honored Professor in the Department of Environmental Atmospheric Sciences, Pukyong National University, Busan 48513, Korea. E-mail: [email protected]. His main research interest is synoptic meteorology, including water resources management, especially on the drought, flood, and water-related seasons.

Claudio Cassardo

CLAUDIO CASSARDO is an Associate Professor in the Department of Physics, University of Torino “Alma Universitas Taurinorum,” Torino, Italy. E-mail: [email protected]. His research interests include climate physics, meteorology, and atmospheric physics in boundary layer using models and data.

Jinmu Choi

JINMU CHOI is a Professor in the Department of Geography, Kyung Hee University, Seoul 02453, Korea. E-mail: [email protected]. His research interests include natural hazard distribution, damage estimation from natural disaster, and environmental deprivation in urban areas.