SiteName

Pearlstone Run

Coordinates

39°31’06”N 76°50’36”W

Study Area Map

# Figure 1: Map of Pearlstone Run sensor placement

Field Observations

Weather and Site Conditions

According to Weather Underground, the Westminster, Maryland weather station (located near the Westminster Radio Tower) recorded 0.00 inches of precipitation during the study period. No rainfall events were documented, indicating consistently dry conditions throughout data collection. The absence of precipitation likely contributed to stagnant stream flow, which also led to us finding a sensor completely dry.

Sensor Images

07/01/25 (Before)

# Figure 2: Initial Sensor images at Pearlstone Run

09/15/25 (After)

# Figure 3: Sensor Images taken upon September 15th, 2025
Sensor Site Conditions
  • Lower Sensor: Sensor exhibited slow flow. It seems recently a large Oak tree had fallen over top of the lower stream causing a plethora of sticks to be in and out of the water. The water was knee deep here but stagnant.
  • Middle Sensor: Sensor exhibited very slow speed and it seems as if one bank was built having a tree roots but the other side of the bank was completely exposed and unprotected. Here there are both sticks and leaves laying on top of the stream bed.
  • Upper Sensor: - Very small and narrow part of the stream. The sensor is surrounded by lush riparian cover making it difficult to get to. This sensor also exhibited blockage of debris which seemed to hinder flow.
Bank Stability and Flow Summary

Not stable banks and almost like a shore with sediments piling up where there isn’t water. More importantly there is a plethora of leaves and sticks within the stream. Flow speeds were slow, no rapid movements along with stagnant dust underwater.

Precipitation

no recorded precipitation during this time

# Figure 4: Temperature over time graph of the entire study period showing the temperature flux of all four sensors.

# Figure 5: Mean daily temperatures recorded by the four iButton sensors (Upper Stream, Lower Stream, Air) across the study period. Values represent the average temperature for each sensor per day, illustrating overall thermal differences among sensor positions.

Wet vs. Dry Data

# Figure 6: Sensor wetness count across the study period. Values represent the amount of days that each sensor was classified as wet. This graph excludes the air sensor.

September 10th close-up (Warming)

Diurnal Temperature Slopes — September 10th (No Precipitation)
Sensor Min_Time Max_Time Next_Min_Time Min_Temp Max_Temp Slope_Up_C_per_hr Slope_Down_C_per_hr
Upstream 2025-09-10 00:40:01 2025-09-10 14:55:01 1757517001 59.169 60.973 0.127 0.000
Middle Stream 2025-09-10 00:10:01 2025-09-10 15:40:01 1757537701 57.478 60.185 0.175 -0.172
Downstream 2025-09-10 00:25:01 2025-09-10 14:10:01 1757535901 58.173 61.777 0.262 -0.144
Air 2025-09-10 00:41:01 2025-09-10 16:11:01 1757548561 53.706 72.629 1.221 -1.046 

# Figure 7:. Hourly temperature changes across all four sensors during the morning–afternoon warming period on September 10th, 2025.

August 1st close-up (Cooling)

Cooling Slopes — August 1 (12 PM to 12 AM)
Sensor Start_Time End_Time Start_Temp End_Temp Cooling_Slope_F_per_hr
Upstream 2025-08-01 16:10:01 2025-08-01 23:55:01 67.281 65.479 -0.233
Middle Stream 2025-08-01 16:10:01 2025-08-01 23:55:01 63.794 62.892 -0.116
Downstream 2025-08-01 16:10:01 2025-08-01 23:55:01 65.380 63.578 -0.233
Air 2025-08-01 16:11:01 2025-08-01 23:56:01 70.828 62.721 -1.046 

# Figure 8: Hourly temperature changes across all four sensors during the afternoon–night cooling period on August 1st.

Analysis

This analysis integrates continuous sensor data with field observations from July to September 2025 to characterize the thermal behavior and hydrologic conditions of Pearlstone Run. The key findings reveal a strong seasonal cooling trend moderated by consistent spatial gradients, significant diurnal dynamics driven by atmospheric influence, and streamflow conditions thriving despite the lack of precipitation for this entire study period.

A clear seasonal cooling trend is evident, with mean water temperatures declining from the high 60s (°F) in early July to approximately 60°F by mid-September. Superimposed on this trend is a consistent and stable spatial thermal gradient:

Upstream consistently records the warmest water temperatures. Downstream is typically cooler than Upstream but warmer than the Middle Stream. Middle Stream is consistently the coolest among the in-stream sensors. The nearly parallel decline of temperature lines indicates that the rate of seasonal cooling is uniform across all sites. The Air sensor exhibits dramatically greater thermal variability than the stream sensors, both in daily swings and overall maxima, frequently reaching temperatures more than 20°F above the stream.

Daytime Warming (Sept 10th): The Air sensor warmed at a rate of 1.221 °C/hr, nearly 5-10 times faster than the stream sensors (0.127–0.262 °C/hr). Nighttime Cooling (Aug 1st): Similarly, the Air sensor cooled at -1.046 °F/hr, a rate 4-9 times faster than the stream sensors (-0.116 to -0.233 °F/hr). This demonstrates the high thermal inertia of water compared to air, buffering stream temperatures from rapid atmospheric changes.

Flow Impediments: All three sensor sites were affected by organic debris (sticks, leaves) and channel characteristics that hindered flow. The Lower sensor site was impacted by a fallen oak tree, the Middle sensor by an exposed, unstable bank, and the Upper sensor by narrow channel geometry and debris blockage. This Implicates that flow stagnation reduces convective heat transfer and mixing, potentially contributing to the observed stable thermal gradients and allowing localized factors (EX: sun exposure on exposed banks, groundwater inputs) to have a more pronounced effect on sensor readings.