1 / 24

Changes in River Special Runoff in Estonia during the Period of Minimum Discharge in Summer 1951-2016

This study examines changes in river special runoff during the summer minimum discharge period in Estonia from 1951 to 2016. It analyzes trends and regime shifts, explores the impact of temperature, snow cover duration, and precipitation, and discusses the implications for drought and water availability in the landscape.

mbarbee
Download Presentation

Changes in River Special Runoff in Estonia during the Period of Minimum Discharge in Summer 1951-2016

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Changes in river specialrunoff in Estonia during the period of minimum discharge in summer 1951-2016 Mait Sepp Zaragoza, 12 February 2018

  2. Changes by trend of mean, maximum and minimum temperature in Estonia in 1966-2010

  3. Snow cover duration in Tartu 1893/95-2014/15

  4. Changes by trend of spatial mean precipitation (mm) in Estonia during 1966-2010 Highprecipitationperiod 1975-2006

  5. Estonian surface runoff in 1924 – 2014 (catchment area 45227 km2) (Ennet, Reihan, Järvet, Pihelgas, 2016)

  6. So, what about the runoff in summer? • Summer runoff as a proxy for drought • Higher air temperature in summer -> higher evaporation -> less water in rivers • Shorter snow cover duration and earlier snowmelt-> less water in spring -> prolonged summer minimum period • But precipitation in summer has increased?

  7. Drasticchanges in winter No changes in summer

  8. What about minimum runoff? • Monthlymeanrunoffcanbeaffectedbyshortbutintensiveflashfloods • Minimumrunoffas a mesure of wateravailability in landscape • Are there any changes in the summer runoff minimum? • Summer minimumrunoffperiod?

  9. Data • Estonian Weather Service • 16 stations + spatialaverage • Dailydata • Period 1951-2016 • Specialrunoff (l/s*km²) • May-August • Lineartrends and regimeshifts • Result: notmuchchanges…

  10. Very few statistically significant trends or regime shifts • Some regime shifts that coinside with 1975-2006 high water period • General tendencies show increase in minimum runoff

  11. Except for May RainyMayorshift in springflood? 6 of 16 stations have negative trend in minimum value

  12. Except for June • 9 of 16 stations show positive trend in monthly mean and minimum runoff June has become rainy

  13. Except for July in small rivers

  14. How to define and analyse summer low water period? Lenght of theperiod and meanvalue

  15. STARS method • Regime shifts • S. N. Rodionov (Uni. Of Washington, Seattle) • NOAA Bering Sea Centre • https://www.beringclimate.noaa.gov/regimes/ • The method is based on the sequential application of the Student's t-test

  16. Significancelevel: 0.1 Cut-offLenght: 30 (days) HWP:1

  17. Lenght: 188 days, Weightedspecial runoff:1.72

  18. It looks nice, however… • Largeinterannualvariance • Differentrivers – differentregimes • i.e. setting 0.1/30/1 isnotuniversal • Results: • No statisticallysignificanttrends • Lenght and weightedspecialrunoff are correlated (r = -0.21…-0.56) • Shortertheperiod, highertherunoff

  19. Tendences In linewithclimatepredictions: Morewater in NorthernEurope Morewater in thesystem. Howmuch?

More Related