Hydrograph, Pollutograph, and Thermograph Analysis ofDeiced Highway Drainage
D.W. Ostendorf, E.S. Hinlein, and C. RotaruEnvironmental and Water Resources Engineering Program
Civil and Environmental Engineering DepartmentUniversity of Massachusetts, Amherst
International Conference on Environmental Science and Technology
American Academy of SciencesHouston, TX June 29, 2012
Overview
• Institutional and physical setting
• Highway drainage system, vadose zone, aquifer
• Linear systems and instantaneous unit hydrographs
• Specific conductivity as deicing agent surrogate
• Temperature as possible third signal
• Conclusions
Hobbs Brook Reservoir Subbasin
Public water supply, Cambridge Water Department
Interstate 95 Right of Way
Interstate 95 right of way (Route 128), maintained by Massachusetts DOT
Deicing Agent Application
Road salt (NaCl) and prewetting (MgCl2) to deice the pavement
Runoff from Closed Drainage System
Curbs, catchbasins, storm sewers: QR, μR
Continuous Discharge and Specific Conductivity
Flow meter, potentiometric probe, and thermometer at 15 minute frequency or faster. Leads to telemetry….
Telemetry and Maintenance
Local power and dedicated landline. To USGS online website…..
USGS <15 Minute Data Base
Hyetograph (P)
Hydrograph (Q)
Pollutograph μ(SpC/major ions).Since SpC is normalizedto 25 deg C, T is alsomeasured, though not commonly reported
Rights of Way and WatershedsStakeholders and Agencies
• Drivers demand* bare pavement and unimpeded driving speeds under all conditions.
• Deicing agents must interact with solid precipitation on the pavement texture.
• Drinking water users demand* low ion concentrations in surface water supply reservoir.
• Four cooperating agencies—MassDOT (I95 deicing), Cambridge Water Department (water supply), USGS (data acquisition), UMass (analysis)
• *these are Boston drivers and Harvard users
Hydrographs-Conservation of Water Mass
Baseflow and interflow are constant during storm. Runoff is absent and baseflow is constant during interstorm period. Runoff and interflow output are IUH convolutions of precipitation (P) input
BIR QQQQ
Discharge is superposition of runoff (closed drainagesystem, interflow (vadose zone), and baseflow (aquifer)
d)]t(exp[)(PACQ I,Rt
I,RI,RI,R 0
RunoffVery intense storm of 6-7 September 2008. Calibrates the closed drainage system decay constant Q~QR
IUH holds for all storms. Note the high discharge response to the storm
141081 sx.R
Hour of 6-7 September 2008
Calibrated value implies a laminar sheet flow depth of 0.5 mm, based on a 0.01 pavement slope and a 100 m distance between catch basins. Note the hourly response time.
InterflowVery intense storm of 15 June 2006, followed by 7 day interstorm period. Calibrates the vadose zone decay constant
This holds for all storms. Note the semilog plot of the hydrograph QI<<QR
161064 sx.I
Days in June 2006
Interflow is slower and weaker than the runoff. Baseflow is slower and weaker than interflow, but is perennial. Note the daily response time of the vadose zone. Baseflow is seasonal.
Andover I495/I93 Autosampler
Some highway sites have autosamplers along with the continuous probes…………..
Ion Chromatograph for Cl-
Water samples may be analyzed for major cations (ICP), anions (IC, TOC), and charge balance………..
SpC to Chloride Correlation
Couples dissolved pollutographs to solid deicing agent dissolution, if chloride is the major anionic constituent (NaCl, MgCl2, CaCl2)
Pollutographs-Conservation of SpC
Baseflow flux constant during storm (QBμB). Interflow flux from plowed drift (QIμI). Runoff flux due to dissolution of (residual) deicing agents on the pavement (μP) into precipitation
QFFF BIR
(Advective) flux F as product of specific conductivityand (water) discharge
d)]t(exp[)()(PACF Rt
PRRR 0
Water and contaminant mass transport are coupled
Deicing Agent Dissolution Kinetics
Elemental volume in the mm scale pavement texture (ζ)
PP P
dtd
Zero order source strength (ω) depends on granule size,which shrinks seasonally. Kinetics determine μP, FR
Specific Conductivity Pollutographs
Winter SpC rises to 7 mS/cm with first flush of runoff. Strong source and comparable interflow and baseflow concentrations.
Summer SpC diluted by runoff, recovers to baseflow asymptote. Weak source, weak interflow, constant (and appreciable!) baseflow concentrations.
scmmSmx
4105
cmmS.;
cmmS. BI 042241
scmmSmx
5102
cmmS.;
cmmS. BI 2420620
Thermographs-Conservation of Energy
Baseflow and interflow temperatures vary sinusoidally to reflect diffusive heat transfer into subsurface
QTQTQTQT BBIIRR
Simplest approach, just mixes the temperature streams
)tsin(TTTT SBI
Runoff varies linearly to mimic cooling (heating) on road
tTT ROR
Just a simple start: no phase change, meteorology, etc.
June 2006
Hyetograph (P), hydrograph (Q), pollutograph (μ), and thermograph (T). Runoff and subsurface are hot
The summer runoff thermograph is reasonably modeled. Subsurface thermograph is periodic.
KT;KT SRO 288293
March 2006Hyetograph (P), hydrograph (Q), pollutograph (μ), and thermograph (T). Runoff and subsurface are cold
The winter runoff thermograph is poorly modeled, though subsurface thermograph is periodic.
KT;KT SRO 277281
Thermograph model doesn’t work. Yet.
Acknowledgments• MassDOT/UMass ISA 56565 funding, with USGS
subcontract to UMass for instrument maintenance and USGS website management.
• Cambridge Water Department logistical support.
• Nonetheless, the analyses and conclusions are only by the Authors. Not a specification or regulation of any Agency, local, state, or federal………….
Conclusions• Classical linear theory describes hydrographs as
single linear reservoirs for closed drainage, vadose zone, and aquifer. Simple, accurate, and physically plausible decay constants.
• Surface runoff pollutograph dominate specific conductivity in winter, much weaker in summer—baseflow is stable and appreciable year round.
• Hydrograph and specific conductivity pollutograph analyses are coupled and well established—and useful for deicing agent fate and transport modeling.
• Thermograph model too simple to recover winter runoff data. As yet unproven.
References (Proceedings Paper)• Gelhar, L.W. and J.L. Wilson, 1974. “Groundwater quality modeling”. Groundwater,
12(6): 399-408.• Granato, G.E. and K.P. Smith, 1999. “Estimating concentrations of road salt
constituents in highway runoff from measurements of specific conductance”. WRI Rept. 99-4077. USGS, Northborough, MA, 22 pp.
• Nash, J.E., 1959. “Systematic determination of unit hydrograph parameters”. J. Geophys. Res., 64(1): 111-115.
• Ostendorf, D.W., D.C. Peeling, T.J. Mitchell, and S.J. Pollock, 2001. “Chloride persistence in a deiced access road drainage system”. J. Environ. Qual., 30(5): 1756-1770.
• Ostendorf, D.W., E.S. Hinlein, D.P. Ahlfeld, and J.T. DeJong, 2006. “Calibrated models of deicing agent solids, pavement texture, and specific conductivity of highway runoff”. J. Environ. Eng., 132(12): 1562-1571.
• Smith, K.P., 2007. “Hydrologic, water quality, and meteorological data for the Cambridge, MA, drinking water source area, water year 2005”. OF Rept. 07-1049. USGS, Reston, VA, 119 pp.
• Waldron, M.C. and G.C. Bent, 2001. “Factors affecting reservoir and stream water quality in the Cambridge, MA drinking water source area and implications for source water protection”. WRI Rept. 00-4262. USGS, Northborough, MA, 89 pp.
