Unit 24

 Floods, droughts — drought indices

This unit looks at extreme situations in the water cycle that are caused by too much or to few precipitation.

The water footprint within the hydrologic cycle (adapted from Salmoral et al., for a normal climatic year (2008) without irrigation allowances restriction. The first value of the water footprint of agriculture corresponds to the consumption during the growing period and the second value to the rest of the year. From: https://www.researchgate.net/profile/Gloria_Salmoral/publication/259216784/figure/fig7/AS:297167869759501@1447861749848/The-water-footprint-within-the-hydrologic-cycle-adapted-from-Salmoral-et-al-13.png

Goals

The goal of this unit is to introduce extreme events of the hydrological cycle and how they are classified.

Photo courtesy to Sean Johnston. 2018

After successful completion of this unit students will be able to

  • Define floods, and droughts
  • Calculate, distinguish and evaluate various drought indices
  • Calculate the 10, 50, 100, and 500 year flood likelihood using the percentile method
  • Explain flood prediction
  • Interpret river forecasts in terms of precipitation, evaporation, green (plant available) and blue (usable for mankind) terms (graduate students)
1979-2010 monthly Global Precipitation Climatology Project (GPCP) precipitation is used to compute the SPI for 12 and 24 month run lengths

Students’ tasks

  1. Work thru this slide show
  2. Read this review article on drought indices
  3. Read Dingman  C.9.2 Regional L-Moment Approach
  4. Take notes and prepare to present the material
  5. Fill out the questionnaire
  6. Compare drought indices,  river forecasts,  long-term river flood risk, and analysis of past droughts via this NOAA web site
  7. Undergraduate students: Post about something that you found interesting, didn’t expect or you just found “cool” when doing the comparison
  8. Graduate students: Write a small summary of what you learned from the comparison (< 1 page) and submit it by the deadline

Useful links and additional material

Standardized Precipitation Index data

Standardized Precipitation Evaporation Index data

Drought monitor

Article by Haddad et al. 2012 on flood reoccurence comparison of flood frequency determination

Free software  to  calculate the SPI

Free software to calculate various drought indices

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