Pequannock River event on 8/23/2021

The following actions were taken by Newark:

  • City personnel were releasing additional water from Oak Ridge Reservoir over the past week in an effort to lower the Oak Ridge Reservoir level.
  • City personnel were monitoring conditions during and after the rainfall from Hurricane Henri.
  • City personnel reduced the low level release to about 25 cfs on Monday (8/23) morning because Charlotteburg Reservoir and Clinton Reservoir were spilling.
  • As of Monday (8/23) afternoon, the water level in Oak Ridge Reservoir was about 1 foot below the spillway elevation.
  • Monday (8/23) night, City personnel monitored the USGS gage and noted that the reservoir began spilling and the river temperature was increasing.
  • City personnel went to the dam and increased the low level release to about 60 to 70 cfs at about 12:45 AM on Tuesday (8/24) morning.
  • City personnel will continue to monitor conditions.

Multiple linear regression analysis with rudimentary step-wise regression was used to understand the relatioship between stream temperature and the coldwater release (CD) indicated by Newark’s records. Dataset was taken from the Pequannock USGS gauge station from the recent storm on August 23-24, 2021:

## 
## Call:
## lm(formula = Aug24$Temp ~ Aug24$Discharge + Aug24$CD, data = Aug24)
## 
## Residuals:
##    Min     1Q Median     3Q    Max 
## -2.408 -2.030 -1.284  2.019  6.650 
## 
## Coefficients:
##                  Estimate Std. Error t value Pr(>|t|)    
## (Intercept)     14.452833   0.763266  18.936  < 2e-16 ***
## Aug24$Discharge  0.018991   0.002489   7.629  3.4e-12 ***
## Aug24$CD        -0.015816   0.029750  -0.532    0.596    
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 2.546 on 139 degrees of freedom
## Multiple R-squared:  0.7353, Adjusted R-squared:  0.7315 
## F-statistic: 193.1 on 2 and 139 DF,  p-value: < 2.2e-16
  • Dependent variable for Pequannock’s discharge (Discharge) at USGS gauge station downstream of Oak Ridge were used because the relationship was significant (p < 0.05) and
  • Dependent variable for coldwater discharge/release (CD) was used because we’re interested in the response of the stream temperature downstream

Stream Temperature = b0 - (0.015816 * Coldwater Release) + (.0018991 * Pequannock CFS)

63 cfs is needed to lower water temperature 1 degree Celcius with 95% confidence interval of 22 to 104 based on the recent storm event.