Ecological flow estimation in Latvian - Lithuanian trans-boundary river basins (ECOFLOW)

2019.02.26 Riga

HHHHabitatabitatabitatabitat modelingmodelingmodelingmodeling results (Lithuania) &results (Lithuania) &results (Lithuania) &results (Lithuania) &Methodology for EMethodology for EMethodology for EMethodology for E----Flow estimationFlow estimationFlow estimationFlow estimation

Tomas Virbickas, biology expert

Bartuva below Skuodas HPP: actual Nb of fish (%) and

modeled habitat suitability

Venta below Kuodžiai HPP: actual Nb of fish (%) and modeled

habitat suitability

≤ 12% of

effective

habitat

3 days

2% (~ 2.4 events per year) 34% (~41.4 events per year)

• A comparison of modeling results with the actual data has proved

that they are really meaningful and can be used to establish

ecological flow.

• The main goal is not only to establish ecological flows for the studied

rivers, but also to propose a methodology for calculating e-flows in

other rivers.

• It is unrealistic to carry out hydromorphological measurements and

sampling of fish in each river stretch below HPP, and determine e-

flows which are essential for the target fish species.

• A simplified methodology should be developed.

• Characteristics of the annual runoff E-flow.

• Some common patterns must be present so that the methodology of

estimation of e-flow in the studied rivers could be extrapolated to

other rivers.

Venta below Kuodžiai HPP

05

1015202530

0 2 4 6 8 1012141618202224

Eff

ectiv

e ha

bita

t, %

Q, m3s

Venta Kuodžiai HPP: Alburnoides bipunctatus

0

20

40

60

80

0 2 4 6 8 10 12 14 16 18 20 22 24

Eff

ectiv

e ha

bita

t, %

Q, m3s

Venta Kuodžiai HPP: Vimba vimba

13.38 m3/s

bad poor moderate good high

0 10.2 0.4 0.6 0.8

STATUS

Q (m3/s)No habitat

0.2 0.4 0.6 0.8

Optimal habitat

Barta

(Skuodas HPP)

Venta

(Kuodžiai HPP)

Venta

(Rudikiai HPP)

Mūša

(Dvariukai HPP)

Lėvuo

(Akmeniai HPP)

Q optimal 1.24 13.38 4.41 2.6 1.74

Q optimal * 0.6 0.74 8.03 2.65 1.56 1.04

(min Q30av winter) (1.69) (17.2) (4.85) (4.03) (2.62)

min Q30medianwinter (1) 1.16 13 3.52 2.35 1.59

min Q30median winter * 0.65 0.75 8.45 2.29 1.53 1.03

Q optimal * 0.6/min Q30median winter * 0.65

1.01 1.05 0.86 0.98 0.99Average:

0.98(1) beforeconstruction of HPP

• Streams have natural regimes with seasonal fluctuations of flow. Native species have evolved

under such conditions, and are adapted to them.

• Discharge in summer period (in LT ~mid June – mid October) is naturally less than discharge

during the spawning season (~ end of April-mid of June for cyprinids and ~end of October-

November for salmonids) and during the wintering period (and rearing period for salmonids;

December-May).

• A flow providing at least good conditions was established for those

fish for which optimum at higher flows is associated with natural

runoff in the winter. In addition, optimal runoff for juveniles and

some small fish species is less than that for adults. The modeling

results indicate this.

• Different e-flow values should be set for the low flow season and

another part of the year.

bad poor moderate good high

0.0 1.0

Q (m3/s)No habitat

0.2 0.4 0.6 0.8

Optimal habitat

0.3

• Low flow in the summer time is a natural phenomenon.

• It is usually much lower than in winter-spring and deviatesstrongly from the flow, which is optimal for adults of manyspecies. But it can be beneficial for juveniles of certain speciesor certain small species.

• For adults, these conditions can be considered poor, but notbad, because they manage to successfully survive this period.

Barta

(Skuodas HPP)

Venta

(Kuodžiai HPP)

Venta

(Rudikiai HPP)

Mūša

(Dvariukai HPP)

Lėvuo

(Akmeniai HPP)

Q optimal 1.24 13.38 4.41 2.6 1.74

Q optimal * 0.3 0.37 4.01 1.32 0.78 0.52

(min Q30av summer) (0.35) (5.78) (1.68) (1.17) (0.68)

min Q30mediansummer(1) 0.31 4.57 1.40 0.91 0.56

min Q30median summer * 0.95 0.30 4.34 1.33 0.86 0.54

Q optimal * 0.3/min Q30median summer * 0.95

0.80 1.08 1.01 1.11 1.03Average:

1.00

(1) beforeconstruction of HPP

Barta* Venta1 Venta2* Mūša Lėvuo

min Q30medianwinter * 0.65 (winter e-flow) 0.75 8.45 2.29 1.53 1.03

min Q30mediansummer * 0.95 (summer e-flow) 0.30 4.34 1.33 0.86 0.54

Currently: min Q30meansummer of 95% or 80%*probability(Q “environmental” )

0.22 1.75 0.39 0.38 0.14

• Different e-flows for the summer and for the rest of the year.

• Late autumn, winter and spring are critical periods for riverine fish because

they are cold-blooded creatures. Change in water T° as well as 0° and ice cover

are stressful for them.

• At least the “good” runoff is especially important during the spawning season.

• A significant reduction in habitat area during critical periods is particularly

harmful for fish and can seriously disturb the reproduction.

Ecological flow estimation in Latvian - Lithuanian trans-boundary river basins (ECOFLOW)

2019.02.26 Riga

Paldies!