Using nocturnal water level fluctuations for estimating seepage from stormwater detention systems

Abstract

Abstract:A simple method, modified from White's method, was developed and verified for estimating seepage from two stormwater detention areas (SDAs) for 2 years, using night-time changes in surface water levels. The SDAs were located in warm sub-tropical Florida where the assumption of negligible night-time evaporation for White's method does not hold true. Daily seepage was estimated using the nocturnal water level fluctuations on no flow days during winter when evaporation losses were insignificant. Specific yield, rather than the composite specific yield, provided accurate seepage estimates. The average annual seepage from the two SDAs was 2.03 m/year. At almost 70% of surface flows, seepage is a significant contributor to regional surface and sub-surface flows. Comparison of seepage estimates from the night-time method (NM) and the water balance (WB) method showed that the NM-based estimates were within the range of the estimates from the WB method. At SDA1, the differences between the NM and WB estimates were 1% and 11%, for the 2 years. The discrepancy between the two estimates became higher (27% and 23%) at SDA2. Larger differences at SDA2 were because of higher error in quantifying pumped inflows for the WB method. Successful performance of NM combined with its low resource (single well monitoring) requirements will help quantify seepage from detention areas and other similar features (e.g. ponds, constructed wetlands) in warmer climates. A scale-up for the Caloosahatchee River basin showed that seepage from SDA's accounted for 15% of annual river flows indicating the importance of seepage in evaluating water and chemical balances.

Hydrologic processes that govern stormwater infrastructure behaviour

“…Crosses show the single‐event or monthly retention variation for the same detention systems ( n = 48). Data compiled from Harper, Herr, Baker, and Livingston, (); Harper, Baker, and Harper (); Daniels et al (); Emerson (); Ayub et al (); Shukla, Shukla, and Annable ()…”

Recovering Nitrogen from Farm-Scale Drainage: Mechanism and Economics

“…Subsurface losses were estimated using the modified White method (White, 1932), as developed by Shukla et al (2015). The modified method relies on two main assumptions: (1) nighttime ET in warm, subtropical south Florida is negligible only in the low-temperature season, and (2) there is no difference in seepage rates between day and night (Shukla et al, 2015).…”

“…The N retentions of 62% and 87% in years 1 and 2, respectively, are based on the assumption that the N mass that did not leave the system through surface flow remained in the SDA (table 1). This is not likely because of significant seepage losses from the SDA (Shukla et al, 2015). Approximately half (45%) of the incoming TN was in the form of organic N (table 1).…”