09/08 CERA Analysis
2025-10-08
SiteName
Conservation and Environmental Research Area
Coordinates
39.2554° N, 76.7107° W
Study Area Map
Field Observations
Weather and Site Conditions
According to Weather Underground, a total of 3.01 inches of precipitation occurred during the study period. The heaviest rainfall took place on Thursday, August 14th, with 1.06 inches recorded. Overall, the site experienced moderate rainfall, which likely contributed to slow stream flow conditions for all sensors.
Sensor Images
07/29/25 (Before)
09/22/25 (After)
Sensor Site Conditions
- Lower Sensor: Located in a shaded area with slow flow and stable banks reinforced by both tree roots and branches. The streambed was visible, and evidence suggested the stream had shifted slightly right, exposing sediment along the left bank.
- Middle Sensor: The flow was extremely slow and the water appeared murky, indicating limited movement and possible sediment buildup from reduced velocity.
- Upper Sensor: The stream-bed was completely dry upon arrival. The sensor rested on moist, muddy soil, likely holding water from previous rainfall events. It was situated on a downward slope stabilized by tree roots in the riparian zone. The sensor was relocated due to the absence of surface flow.
Wildlife Observed
- North Carolina Box Turtle
- White-tailed Deer
Bank Stability and Flow Summary
All sensor locations exhibited moderately to highly stable banks supported by dense riparian vegetation and steep slopes that formed a natural ravine. Overall, flow speed was extremely slow across the study area—fastest at the downstream (Lower) sensor and nonexistent at the Upper sensor.
Analysis
This analysis evaluates temperature and hydrologic behavior across four sensor locations (Air, Upstream, Middle Stream, Downstream) within the Chesapeake Bay watershed from July 24 to September 8, 2025. The primary objective is to assess flow permanence through thermal patterns and temperature change rates. Understanding these dynamics is critical for identifying perennial, intermittent, and ephemeral flow segments, which determine eligibility for protection under the U.S. EPA’s jurisdictional definitions of “Waters of the United States.”
Precipitation Data
(p1 | p2) + plot_layout(widths = c(1, 1))
Precipitation and Wet Frequency
There are several isolated storm events producing up to 1.2 inches of rainfall. The Wet Frequency by Sensor data indicate strong spatial variability in hydrologic persistence. The Upstream sensor maintained wetness the most consistently across the study experiment. This sensor exhibited more stable base flow conditions and stronger hydraulic connections to perennial flow. In contrast, Downstream locations exhibited more dry days than any of the submerged sensors, suggesting flow loss and declining groundwater inputs during extended dry periods. This is an odd sighting since normal streams experience more flow as it travels downstream but this shows a hydrologically inverted pattern. This spatial trend doesn’t aligns with the expected flow gradient in headwater systems. The downstream reaches transition toward intermittency, while upstream are the most hydrologically active.
Slope Stats
{No Precipitation} (September 1st close-up)
| Sensor | Period | Start | End | Start_Temp | End_Temp | Slope_C_per_hr |
|---|---|---|---|---|---|---|
| Air | Daytime | 2025-09-01 06:00:00 | 2025-09-01 18:00:00 | 55.575 | 76.297 | 1.727 |
| Air | Nighttime | 2025-09-01 18:00:00 | 2025-09-02 06:00:00 | 75.397 | 57.378 | -1.502 |
| Downstream | Daytime | 2025-09-01 06:00:00 | 2025-09-01 18:00:00 | 59.151 | 68.165 | 0.751 |
| Downstream | Nighttime | 2025-09-01 18:00:00 | 2025-09-02 06:00:00 | 67.264 | 60.053 | -0.601 |
| Middle Stream | Daytime | 2025-09-01 06:00:00 | 2025-09-01 18:00:00 | 61.000 | 69.105 | 0.675 |
| Middle Stream | Nighttime | 2025-09-01 18:00:00 | 2025-09-02 06:00:00 | 69.105 | 61.900 | -0.600 |
| Upstream | Daytime | 2025-09-01 06:00:00 | 2025-09-01 18:00:00 | 59.151 | 68.165 | 0.751 |
| Upstream | Nighttime | 2025-09-01 18:00:00 | 2025-09-02 06:00:00 | 67.264 | 60.955 | -0.526 |
Non-Precipitation Event Response
The table above exhibits temperature change rates calculated for September 1, a representative dry period with no rainfall influence. The Air sensor exhibited the highest diurnal slope magnitude with daytime warming rates of +1.73 °F/hr and nighttime cooling of −1.50 °F/hr, reflecting rapid atmospheric fluctuations. From the graph air also exhibits the widest temperature swing. Stream sensors showed substantially lower slope magnitudes (0.5–0.8 °F/hr) ranges. The slopes confirm that thermal responses increases with stream disconnection. As water depth and flow permanence decline, temperature fluctuations more closely mimic atmospheric patterns.
{Precipitation day} (August 14th close-up)
| Sensor | Period | Start | End | Start_Temp | End_Temp | Slope_C_per_hr |
|---|---|---|---|---|---|---|
| Air | Daytime | 2025-08-14 06:00:00 | 2025-08-14 18:00:00 | 70.895 | 76.297 | 0.450 |
| Air | Nighttime | 2025-08-14 18:00:00 | 2025-08-15 06:00:00 | 78.097 | 70.895 | -0.600 |
| Downstream | Daytime | 2025-08-14 06:00:00 | 2025-08-14 18:00:00 | 68.165 | 73.568 | 0.450 |
| Downstream | Nighttime | 2025-08-14 18:00:00 | 2025-08-15 06:00:00 | 73.568 | 69.065 | -0.375 |
| Middle Stream | Daytime | 2025-08-14 06:00:00 | 2025-08-14 18:00:00 | 72.707 | 76.307 | 0.300 |
| Middle Stream | Nighttime | 2025-08-14 18:00:00 | 2025-08-15 06:00:00 | 76.307 | 72.707 | -0.300 |
| Upstream | Daytime | 2025-08-14 06:00:00 | 2025-08-14 18:00:00 | 69.966 | 72.668 | 0.225 |
| Upstream | Nighttime | 2025-08-14 18:00:00 | 2025-08-15 06:00:00 | 72.668 | 70.867 | -0.150 |
Precipitation Event Response
This data corresponds with the day that exhibited the most precipitation.There is a general smaller diurnal change among all of the sensors.The upstream sensor experienced the least temperature change during the night time diurnal change exhibiting a -0.150 slope. The result tells us that their could be very low runoff and steadybaseflow at the headwaters of this stream. This is also evident from the graph close-up, the temperature plots reveal pronounced cooling visibly lower rates of change.The Air temperature sensor peaked near 84 °F, while stream temperatures remained 3–5 °F lower and exhibited dampened diurnal swings. This pattern indicates enhanced groundwater recharge and increased flow connectivity following precipitation. This precipitation stabilization suggests temporary recovery of flow permanence, particularly at the middle and upstream locations.
Daily Temperature Mean Interpretation
This final graph shows the gradient of thermal temperature mean fluctuion for each sensor throughout the test period. Stream sensors stayed overall cooler than the air temperature and the dips in temperature shown in late July and early August are a reflection of major precipitation events that’s occured. Another note is that the middle stream mean more closely resonates with the air monitoring more than any other senor. This could be a sign of transitional intermittancy where the stream slows down.
Implications for Flow Permanence
Thermal and wet frequency analyses reveal clear spatial gradients in hydrologic behavior across the study.
- Downstream: Despite being located at the lowest point of the system, the downstream sensor exhibited more frequent drying than expected for a typical perennial reach. This suggests potential flow loss from infiltration or disconnection from groundwater inputs during extended dry periods. This section may retain flow only after rainfall events.
- Middle Stream: The close thermal tracking with air temperatures and moderate slope magnitudes suggest intermittency, where flow is sustained primarily by short-term runoff or shallow groundwater discharge following precipitation.
- Upstream: Contrary to expectations, the upstream sensor maintained the most consistent wetness and smallest thermal response during precipitation, indicating strong groundwater influence and stable baseflow. This reach appears to be hydrologically buffered and potentially perennial, despite being the headwater section.