Seppo Hellsten & Teemu Ulvi Oulujoki Pilot River Basin – Provisional Designation of Heavily Modified Rivers and Lakes Seppo Hellsten & Teemu Ulvi

area 22 841 km2 lake percentage 11.4 % mean annual discharge 259 m3/s number of lakes 502 number of rivers 85

Introduction Typical representative of Nordic problems Relatively good water quality and a lot of pristine waters Scarcity of population > less than 12 inh./km2 Few point source pollution – usually under control Diffuse loading from agriculture and forestry Extensive use for hydropower with parallel benefit for flood defence Hydropower production plays important role by modifying water bodies smaller modifications caused by clearing of rivers for timber floating hydromorphological pressures are playing an important role 9.9.2019

Eutrophic lakes in Oulujoki Catchment (Lepistö et al., 2000) 9.9.2019

Regulated lakes and hydropower plants # 5 1 K i l o m e t r s N 18 plants > 550 MW 1400 km2 regulated lakes construction efficiency > 80 % N 9.9.2019

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GENERAL VIEWS OF HYDROMORPHOLOGICAL PRESSURES OF RIVER OULUJOKI Morphological changes are poorly documented and general database is not available Projects have taken place a long time ago => timber floating, drainage works, flood protection, hydropower A lot of manual works needed Hydrological databases are covering largest lakes and main rivers Recalculated natural values and on-line data are available A proper basis for estimation ASSUMPTION: Morphological pressures plays significant role in small rivers, hydrological in larger ones and lakes 9.9.2019

How to find a simple HyMO-pressure estimation procedure? Needed factors should be determined: Hydrological status Morphological status River continuum Estimation procedure should be realistic and without any extra financial demands Multiphase approach 9.9.2019

APPROACH FOR IDENTIFICATION HyMo PRESSURES AND HMWBs PHASE 1: IDENTIFICATION OF PRESSURES (PRE-SCREENING) Pressures are identified and their significance are estimated in a broad scale (expert judgement) WBs where HyMo- pressures are of minor importance WBs where HyMo- pressures are non-significant PHASE 2: ASSESSMENT OF THE PRESSURES Further analysis of significance of pressures based on the HyMo criteria Data collection PHASE 3: PROVISIONAL DESIGNATION Criteria for regulated and constructed lakes and rivers Provisonally heavily modified WBs

RIVERS PHASE 1. IDENTIFICATION OF PRESSURES (PRE-SCREENING) No pressures (class 0), minor pressures (class A), significant pressures (class B)

PHASE 2: ASSESSMENT OF THE PRESSURES

PHASE 3: PROVISIONAL DESIGNATION (HCMo-model) Listing of Hydrological, Continuity and Morphological indices from phase 2 Calculation of alteration indices (AI) AI = (Hi/n+ Ci/n + Moi/n)/3, where H=hydrological factors (i= 1-n), C = continuity factors (i= 1-n) Mo = morphological factors (i= 1-n) and n = total amount of alteration factors. 9.9.2019

Changes Scoring HYDROLOGY CONTINUITY MORPHOLOGY Alteration index 10 River Muhosjoki 59 km Changes Scoring name of project, detalls Very sign. change=4, sign. change =3, moderate=2 small change=1, no change=0 HYDROLOGY A. Mean discharge change (MQ) - B. Change in daily discharge change in flood peak 1 C. Change in flood peak CONTINUITY A. Dams and weirs – other factors preventing animal and sediment movement 8 weirs and bridges 3 MORPHOLOGY A. Changes in structure of river bed Dredging 2 B. Longitudial changes (meanders etc.) cut-offs C. Bank changes embankmentst Alteration index 10 Out of maximum value 27.8

Comparison HCMo / RHS River Muhosjoki 100.0 y = 1.9833x + 3.371 80.0 R 2 = 0.8976 60.0 HCMo (%) 40.0 20.0 0.0 0.0 10.0 20.0 30.0 40.0 50.0 HMS (%) 9.9.2019 Comparison HCMo / RHS

Preliminary results Main stream of River Oulujoki is provisionally designated as HMWB Smaller rivers are not significantly modified 9.9.2019

LAKES Similar three phase approach Morphological pressures are evaluated only in lakes smaller than 10 km2 Hydrological pressures are the most important in large lakes 9.9.2019

Typical lake regulation

PHASE 3. IDENTIFICATION OF HMWBs 1. step Classification of lakes based on lake-percentage of watershed 2 criteria; winter draw-down and extension of spring flood WATER LEVEL FLUCTUATION SIMILAR TO NATURAL WATER LEVEL FLUCTUATION DEVIATING FROM NATURAL NATURAL WATERBODY LAKES WITH HIGH HYDROLOGICAL STATUS Result: 20 % of 105 regulated lakes were at high hydrological status WATER LEVEL FLUCTUATION IN NON-REGULATED LAKES

IDENTIFICATION OF HMWBs 2. step Classification of lakes based on lake-percentage of watershed 2 criteria; winter draw-down and extension of spring flood WATER LEVEL FLUCTUATION SIMILAR TO NATURAL WATER LEVEL FLUCTUATION DEVIATING FROM NATURAL MAGNITUDE OF DEVIATION 3 criteria; water-level raise/draw-down, winter draw-down and extension of spring flood NO FILLED CRITERIA AT LEAST ONE CRITERIA FILLED NATURAL WATERBODY Results: 10 lakes of 42 deviated with low values 4 lakes of 42 deviated with high values CRITERIA Increase in winter draw-down 1,5 m or 3 m Decrease in spring flood 0,7 m or 1,2 m Increase/decrease in mean water > 1 m

MACROPHYTES (LARGE ISOETIDS) COMPOSITION > 3 metres GOOD MODERATE ZOOBENTHOS COMPOSITION > 3 metres REGULATED LAKES NATURAL LAKES

Preliminary results HMWB-lakes With strict criteria: Lakes Vuokkijärvi and Iso-Pyhäntä With mild criteria: Lakes Ontojärvi and Kiantajärvi Some borderline cases 9.9.2019

Conclusions Provisional designation gives relatively similar results than expert judgement Biological response is especially in rivers unclear biological classification is still missing difficult to distinguish different pressures in rivers 9.9.2019