John Dinnall

Site Description

Catchment: The Conservation and Environmental Research Area (CERA) is a suburban headwater stream in Baltimore County, Maryland (39°14’43”N, 76°42’46”W) on the campus of the University of Maryland, Baltimore County. This catchment drains approximately 0.45 square miles of mixed suburban and secondary forest land cover within a narrow, partially forested riparian corridor. The catchment drains a portion of an interstate highway spur constructed in the 1980s.

Sensor Deployment: Three in-stream sensors were deployed at Downstream, Midstream, and Upstream positions with a fourth Air sensor mounted to a tree as a dry atmospheric reference. The Upstream sensor was mounted within a cobble-bedded reach with shallow surface flow. Midstream was fully submerged in a deeper, well-shaded riparian zone. The Downstream position exhibited active flow with the widest channel cross-section of the three monitored locations.

Goal: To document flow patterns in this watershed and assess whether low-cost thermal sensing is a viable approach for detecting subsurface flow activity and flow permanence.

Study Area Map

Figure 1: Study area map of CERA Run, Baltimore County, Maryland. Sensor points indicate the locations of the Upstream, Midstream, and Downstream in-stream temperature loggers deployed along the longitudinal transect. The inset map shows the location of CERA Run relative to all study sites within the Baltimore County area.

Figure 2: Daily precipitation recorded at CERA Run from July 2025 through May 2026.

Figure 3: Stacked bar chart showing the proportion of days classified as wet (blue), dry (red), and uncertain (gray) for each sensor position at CERA Run across the full study period.

Figure 4: Daily wetness state classifications for all sensor positions across CERA Run from July 2025 through May 2026. Each row represents a sensor position (Air, Downstream, Midstream, Upstream). Blue indicates wet, red indicates dry, and gray indicates uncertain classifications.

Sensor Images

09/22/25

Figure 5: September deployment shows the site during the late summer. All sections of the stream show wetness and riparian cover throughout the catchment.

11/24/25

Figure 6: November deployment shows the sensor during the autumn and closer to the winter season. Downstream has lost the cover that it initially maintained during the summer. All parts of the stream are wet, but midstream has accumulated large amounts of fall leaves.

01/06/26

Figure 7: January deployment shows how mid-winter affects the water surface flow. Both upstream and midstream are in frozen water; specifically, the midstream is clogged with leaves at the sensor location.

02/27/26

Figure 8: February deployment shows how late winter affects the water surface flow. As in the January photos, upstream and midstream still show frozen water, while downstream continues to flow.

05/20/26

Figure 9: May deployment shows the effect of the spring season. Vegetation has grown since the last deployment, along with moderate baseflow across the entire stream.

Thermal Overview Plots

Figure 10: Hourly temperature recorded by all four sensors at CERA Run from July 2025 through May 2026. The Air sensor (red) reflects ambient atmospheric conditions, while the three in-stream sensors (color coded beside the graph) reflect channel thermal conditions at each longitudinal position. In-stream water temperatures begin in the low-mid 70s, but by January they drop to the high 20’s, while the air sensor shows larger temperature swings and descends to single digits in late January, early February.

Figure 11: Daily mean temperature for all four sensors at CERA Run from July 2025 through May 2026. Averaging hourly readings to a daily mean smooths short-term fluctuations and reveals seasonal temperature trends across the monitoring period.

Case studies

Purpose: To illustrate sensor response during different atmospheric and seasonal conditions. Each case study presents a four-panel diagnostic plot followed by a dryness score table for a single selected day.

4-Panel Plots: A four-panel diagnostic figure showing each sensor’s thermal behavior over 24 hours.

Dryness Score table: A summary of each sensor’s thermal classification for the selected day.

August 14, 2025 (Precipitated summer day)

Figure 12: Four-panel diagnostic plot for August 14th, 2025. Temperatures ranged from 73–90°F, with 1.06 inches of rainfall arriving between 3–4 PM. All sensors remained thermally stable and classified as wet throughout the day.

Dryness Scores — August 14th, 2025
Sensor warming_score cooling_score daily_score conflict_flag wetness_state
Air 1e+00 1e+00 1e+00 FALSE dry
Downstream 4e-04 2e-04 3e-04 FALSE wet
Midstream 0e+00 0e+00 0e+00 FALSE wet
Upstream 4e-04 2e-04 3e-04 FALSE wet

Table 1: A summary of August 14th’s sensor’s thermal classification. There was no conflict flag exhibited among the sensors and all in-stream sensors classified as wet coinciding with the afternoon rainfall.

July 30th, 2025 (Normal summer day)

Figure 13: Four-panel diagnostic plot for July 30th, 2025. Temperatures ranged from 75–94°F, with winds up to 10mph. The Upstream sensor rose approximately 8°F above its morning minimum which is a substantially larger fluctuation than the Midstream and Downstream sensors resulting in an uncertain classification at that position. The daily dryness scores reflect a clear longitudinal gradient, with the Upstream sensor recording the highest dryness score among the in-stream positions and the Downstream sensor recording the lowest, consistent with increasing thermal regulation moving downstream through the monitored reach.

Dryness Scores — July 30th, 2025 (Longitudinal Gradient)
Sensor warming_score cooling_score daily_score conflict_flag wetness_state
Air 1.0000 1.0000 1.0000 FALSE dry
Downstream 0.0000 0.0000 0.0000 FALSE wet
Midstream 0.5006 0.0000 0.2503 TRUE wet
Upstream 0.5006 0.5003 0.5004 FALSE uncertain

Table 2: A summary of July 30th’s sensor’s thermal classification. Notably the midstream sensor did receive a conflict flag due to its higher warming score of 0.5 and the abruptly low cooling score of 0. Overall this reading reflects a longitudinal gradient, with upstream being classified as uncertain (the driest sensor), all the way to downstream, scored 0.0, indicating the strongest wet signal recorded on this date.

December 14th, 2025 (Precipitated winter day)

Figure 14: Four-panel diagnostic plot for December 14th, 2025. Temperatures ranged from 17–36°F with 1/2 an inch of snow. Temperatures at all stream sensors remained relatively stagnant throughout the day. The Air sensor dropped well below freezing while stream sensors remained near 32°F throughout the day.

Dryness Scores — December 14th, 2025
Sensor warming_score cooling_score daily_score conflict_flag wetness_state
Air 1e+00 1e+00 1e+00 FALSE dry
Downstream 3e-04 2e-04 2e-04 FALSE wet
Midstream 6e-04 2e-04 4e-04 FALSE wet
Upstream 0e+00 0e+00 0e+00 FALSE wet

Table 3: A summary of December 14th’s sensor’s thermal classification. All three stream sensors scored within thousandths of zero, indicating near-complete thermal buffering by surface water at every in-stream position. The Air sensor scored 1.0 as expected. No conflict flags were triggered.

December 10, 2025 (Normal winter day)

Figure 15: Four-panel diagnostic plot for December 10th, 2025. Temperatures ranged from 30–45°F, with overcast skies and wind gusts up to 13 mph. All three stream sensors were classified as wet, with no conflict flags. The Air sensor rose approximately 12°F above its morning minimum while stream sensors rose only 3–5°F, demonstrating how in-stream water temperatures remain stable even as atmospheric temperatures fluctuate under winter conditions.

Dryness Scores — December 10th, 2025 (Longitudinal Gradient)
Sensor warming_score cooling_score daily_score conflict_flag wetness_state
Air 1.0000 1.0000 1.0000 FALSE dry
Downstream 0.0006 0.2000 0.1003 FALSE wet
Midstream 0.0011 0.0000 0.0006 FALSE wet
Upstream 0.0000 0.1997 0.0999 FALSE wet

Table 4: A summary of December 10th’s sensor’s thermal classification. All three stream sensors were classified as wet with no conflict flags. Air scored 1.0 because its diurnal temperature swing remained responsive to atmospheric temperatures while the stream sensors stayed thermally regulated by water.

Analysis

CERA maintained consistent surface water presence across all deployment windows, with Downstream and Midstream sensors classifying wet above 85% of days throughout the study period. The overall dryness heat map confirms persistent flow at all three in-stream positions from July 2025 through May 2026, with no dry periods observed at any sensor location. Conflict flags occurred primarily on precipitation days and thermally complex days. Spring conditions increased precipitation frequency and elevated temperatures, producing higher uncertainty counts, particularly at the downstream end of the heat map. Based on thermal patterns observed at the three monitored positions, each sensor location maintained surface water presence across all seasons with no seasonal drying detected at any sampled point. These findings suggest perennial flow conditions at the monitored locations, though the broader stream reach would require additional spatial sampling.