Jan 27, 2010 ... Tuni Dam. Today's Presentation: Basic Methods from our previous studies in.
Lakes and Reservoirs. Tuni Reservoir. Basin of Tuni Reservoir ...
Environmental Hydrodynamics in Lakes and Reservoirs M. Umeda (Tohoku University)
Introduction For the group of Water Quality, Tuni Reservoir = one of Main Research Objects Tuni Reservoir
Basin of Tuni Reservoir Condoriri
Tuni
Tuni Dam
http://maps.google.co.jp
HPW
500m
Today’s Presentation: Basic Methods from our previous studies in Lakes and Reservoirs.
Measurements in Miharu Reservoir General Information Catchment: 226.4 km2 Capacity: 4.2×106 m3 Purpose: Flood control, Water supply, Industrial water, Irrigation, Power generation Sendai Eutrophication Problems Water Bloom, every summer (cyanobacteria) Miharu Reservoir
Field Measurements in a Reservoir Plan view of Miharu
What we measure: a) Stratification Thermal stratification, Vertical distribution of WQ
C A
B D
b) Temporal change of WQ
Dam 0
1.0 km
water temperature, DO, Chlorophyll-a, etc.
c) Deposition flux Including Sediment, Detritus, etc.
Field Measurements in a Reservoir How we measure: a) Stratification (Vertical distribution) Hanging and sinking sensors from a boat. b) Temporal change of WQ Deploying self-recording devices on ropes with floats c) Deposition flux
Buoy Self-recording device Sediment traps
Thermocline
Buoy Sediment traps
Using sediment traps deployed
Sediment traps Anchor
Examples of Results - In Miharu Reservoir-
Turbidity Chlorophyll-a DO
Aug. 5, 2008
10 20 30 0 0
Depth [m]
Water temp.
10
20
0
5
10
15
10
Aug. 14, 2008
20 30 0 0
Depth [m]
a) Stratification (Vertical distribution)
Depth [m]
0
10
20
0
5
10
15
Sep. 5, 2008
10 20 30 0
10
20
WT [oC] Turbidity
0
5
10
Chl-a [µg/l] DO [mg/l]
15
WT [oC]
320
12
310
8 4
DO [mg/l]
DO
300
30 20 10 0
320 310
300
0
320
40
Turbidity 310
20
300
0
Jan.
Apr.
Aug.
Dec.
[FTU]
Water Temp.
Altitude[m] Altitude[m]
b) Temporal change of WQ (Measurement by the Dam Office, MLIT) History of vertical distributions
Hydraulic Numerical Modeling Solvers are selected depending on requirements: Spatial Resolution 1-dimensional (vertical) 2-dimensional (vertical) 3-dimensional
Simple, but sometimes gives more realistic solution than higher dimension analysis
Variables Water temperature related to density structure. Turbidity Salinity Chlorophyll-a (phytoplankton) Nutrients (Phosphorus, Nitrogen) related to eutrophication. Dissolved Oxygen
Example of Computation Vertical 1-D Modeling in a coastal lagoon Conceptual diaguram of Vertical 1-D Model Outflow
Lake Jusan
0 1 2km
Inflow
Famous for product of shelfish Lake Jusan: Facing the Japan Sea Very shallow lagoon: Mean depth = 1m
Results: Validation of Time Series Vertical 1-D computation 300 Discharge 200 100 [m3/s] 0 Salinity 1 30 20 10 [psu] 0 Salinity 2 30 20 10 [psu] 0 10 DO 5 [mg/l] 0
6/9
7/7
Blue line: Measurement Red line: Computation
8/5
9/1
Results: History of Vertical Structure
Elevation[m]
Elevation[m]
Vertical 1-D computation 1
Freshwater (white)
Salinity
0
Saline water (blue)
−1 1
DO
0
High DO (white)
−1
Jun. 9
Jul. 7
Aug. 5
Sep. 1 Oct. 6 Low DO (Red)
Numerical Modeling Solvers are selected depending on requirements: Spatial Resolution 1-dimensional (vertical) 2-dimensional (vertical) 3-dimensional
Most often used in practical works
Variables Water temperature related to density structure. Turbidity Salinity Chlorophyll-a (phytoplankton) Nutrients (Phosphorus, Nitrogen) related to eutrophication. Dissolved Oxygen
Method of 2-D analysis The most typical modeling for reservoirs. Vertical 2-D Reservoir Hydrodynamic Model Water temp. Velocity
Inflow
outflow
Governing Equations •Momentum Eq. •Continuity Eqs •Transport Eqs of scalars •K-ε turbulence model Eqs
∂u ∂u ∂u 1 ∂p 1 ∂ ∂u ∂ ∂u +u +v = − + ν L B ν eff B ρ ∂x B ∂x ∂t ∂x ∂y ∂x ∂z ∂z ∂ ∂ 0 , etc.. ( uB ) + ( wB ) = ∂x ∂z
Including the bathymetry effect of breadth B.
Longitudinal & Vertical Distribution of Suspended Sediment From an Investigation of High Turbidity Problem Caused by Flood Water Intrusion Upstream
Dam Altitude (m)
320 300 280 260 0
0.5
1
1.5
Distance (km)
10 20 30 40 50 60 SS [mg/l]
Water Quality in Miharu Reservoir Lines: Computation, Dots: Measurement 60
Chlorophyll – a (µg/l) 40 20
Inorganic Phosphorus (mg/l) Inorganic Nitrogen (mg/l)
0 0.04 0.03 0.02 0.01 0 2 1.5 1 0.5 0
May
July
Sep. 2008
Summary • Basic research methods for environmental hydraulics in lakes and reservoirs were presented. • Field measurements in Miharu Reservoir was shown as a typical example. • Water quality numerical modeling s in a coastal lagoon (case of 1-D) and a reservoir (2-D) were demonstrated.
