Hydromorphology of Two Urbanizing Watersheds
Melissa NgMaster’s Candidate
Civil and Environmental EngineeringTufts University
Hydromorphology
The study of the changes in the hydrologic system.
Stationary systems are“natural systems that fluctuate within an unchanging envelope of variability”-Milley 2008
Non-stationarity
“The stationarity assumption has long been compromised by human disturbances” – Milley, 2008
Non-stationarity: Urban Watershed
Aberjona River Flow Duration Curve
0.1
1
10
100
1000
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00
Exceedence Probability
Flow
(cfs
)
1940-19691970-2007
Aberjona River Streamflow
Increase in flow regime
Understand the impact that climate and human activities have on streamflow
Develop planning tool for dealing with non-stationarity of streamflow
Study Goals
Case Studies: Aberjona River WatershedNeponset River Watershed
Population Changes 1940-2008
0
4
8
12
16
1940 1950 1960 1970 1980 1990 2000 2010Year
Pop
ulat
ion
(tho
usan
ds)
Neponset River watershedAberjona River watershed
Case Studies: Aberjona River WatershedNeponset River Watershed
Aberjona River Watershed Neponset River Watershed
• Traditional approach assumes stationarity• Generates possible realizations of future
streamflowQt = f(Qt-k)
Qt = streamflow at time tQt-k = streamflow at time t-kk = lag
• Water Resources planningWater quality modeling, Reservoir Planning, Irrigation planning,
Hydropower, etc.
Current Planning Tools:Stochastic Streamflow Modeling
Current software packages: HEC-4, SPIGOT, SAMS
Application
Sveinsson, et al., 2003
Aberjona River Flow Duration Curve
0.1
1
10
100
1000
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00
Exceedence Probability
Flow
(cfs
)
1940-19691970-2007
Aberjona River Streamflow
Increase in flow regime
Neponset River Flow Duration Curve
1
10
100
1000
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00Exceedence Probability
Stre
amflo
w (c
fs)
1940-19691970-2007
Neponset River Streamflow
Increase in high flowsDecrease in low flows
Causes of Nonstationarity
30
40
50
60
70
1985 1990 1995 2000 2005Year
Prec
ipita
tion
(in) Aberjona River Basin
Neponset River Basin
0
500
1000
1500
2000
1935 1945 1955 1965 1975 1985 1995 2005Year
Lan
d U
se (A
cres
)
Aberjona River basinNeponset River basin
2,000
2,500
3,000
3,500
1985 1990 1995 2000 2005Year
With
draw
al (m
gal)
1,000
1,500
1985 1990 1995 2000 2005
Year
With
draw
al (m
gal
Aberjona River watershed withdrawals Neponset River watershed withdrawals
Precipitation Land Use (Impervious Area)
• Models include exogenous variables• Exogenous variables: Precipitation, land use, water
withdrawal
ln Qt = a0 + Σb1lnQ(t-k) + Σ c 1lnX (t-k) + εt
Qt = streamflow at time tx(t-k) = exogenous variable at time t-kk = lag
Multivariate Non-stationary Stochastic Streamflow model
Model Results: Physical implications
ABERJONA RIVER MODEL
ln Q(m,y) = 11.045 + 0.521ln Q(m-1,y) + 0.225ln Q(m,y-1)
+ 0.872ln P(m,y) - 0.156ln P(m,y-1) – 0.578ln W(m,y)
Monthly streamflow:
-increases with increasing previous streamflow and contemporaneous precipitation
-decreases with increasing water withdrawal
Model Results: Physical implications
NEPONSET RIVER MODEL
ln Q(m,y) = 11.045 + 0.614ln Q(m-1,y) + 0.196ln Q(m,y-1)
+ 0.747ln P(m,y) - 0.175ln P(m,y-1)
-0.917ln LU(y) – 0.761ln W(m,y) – 0.576ln W(m,y-1)
Monthly streamflow:
-increases with increasing previous streamflow and contemporaneous precipitation
-decreases with increasing land use and water withdrawal
Model Results: Interaction of variables improves explanatory power of the model
ABERJONA RIVER MODEL
Variables Adjusted R2
Streamflow 31.50
Streamflow,Precipitation 79.00
Streamflow,Precipitation,Withdrawal 80.90
NEPONSET RIVER MODELVariables Adjusted R2
Streamflow 47.60
Streamflow,Precipitation 79.80
Streamflow,Precipitation,Land use 79.80
Streamflow,Precipitation,Withdrawal 83.40
streamflow,precipitation,Land use, Withdrawal 83.70
1. Historical streamflow is not adequate alone, to forecast future streamflow
2. Precipitation, landuse and water withdrawal cause changes in streamflow
3. Interactions among water balance components are important
4. Stationarity is Dead in an urban environment!
Summary
Thesis committee:
Dr. John Durant (Tufts University, CEE)
Dr. Chuck Kroll (SUNY-ESF)
Dr. Rich Vogel (Tufts University, CEE)
Dr. Jeff Zabel (Tufts University, Dept of Economics)
Acknowledgements