Site Description

Catchment: Senior Run is an urban headwater stream in Baltimore County, Maryland (39°16’43”N, 76°45’01”W), draining 0.16 square miles of residential land cover dominated by mowed turf and scattered trees. The headwaters originate in a parking lot, reflecting a highly impervious contributing drainage area typical of urbanized Piedmont catchments.

Sensor Deployment: Three in-stream sensors were deployed at Downstream, Midstream, and Upstream positions with a fourth Air sensor mounted as a dry atmospheric reference. The Downstream position showed active flow. Midstream was fully submerged within a developed riparian zone. The Upstream position exhibited saturated soils and dense skunk cabbage with the sensor at surface water level.

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 Senior 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 Senior Run relative to all study sites within the Baltimore County area.

Figure 2: Daily precipitation recorded at Senior 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 Senior Run across the full study period.

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

Sensor Images

09/09/25

Figure 5: September deployment shows the site during the late summer. The Upstream position showed reduced surface water coverage relative to Midstream and Downstream during the late summer deployment.

11/25/25

Figure 6: November deployment shows the sensor during the autumn and closer to winter season. The Midstream and Downstream sensors remained fully submerged, while the Upstream position continued to show reduced surface water coverage.

01/07/26

Figure 7: January deployment shows how mid-winter effects the water surface flow. The image here shows upstream experiencing the most flow out of any of the previous images. Midstream and downstream continue to experience consistent flow.

05/20/26

Figure 8: May deployment shows the effect of the Spring season. The upstream sensor is surrounded by tall grass and skunk cabbages which are known to absorb lots of water. The water surface isn’t visible at the upstream position due to the overgrowth of surrounding plants.

Thermal Overview Plots

Figure 9: Hourly temperature recorded by all four sensors at Senior Run from July 2025 through May 2026. The Air sensor reflects ambient atmospheric conditions while the three in-stream sensors reflect channel thermal conditions at each longitudinal position. In-stream water temperatures begin in the low-to-mid 70s°F in summer before declining toward freezing by January, while the Air sensor exhibits considerably larger diurnal swings throughout the monitoring period.

Figure 10: Daily mean temperature for all four sensors at Senior 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. Convergence between Air and stream sensor temperatures may reflect overcast, cool, or rainy conditions suppressing diurnal contrast rather than reduced surface water presence.

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 a 24-hour period.

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

August 14th, 2025 (Summer rainfall day)

Figure 11: Four-panel diagnostic plot for August 14th, 2025. Temperatures ranged from 73–90°F with 1.06 inches of rainfall arriving between 3–4PM. The Upstream sensor warmed rapidly in the morning before the precipitation event abruptly cooled the atmosphere, triggering a conflict flag at that position. Midstream and Downstream remained thermally stable and classified wet throughout the day.

Dryness Scores — August 14th, 2025
Sensor warming_score cooling_score daily_score conflict_flag dryness_state
Air 0.5707 1.0000 0.7853 FALSE dry
Downstream 0.0000 0.1111 0.0555 FALSE wet
Midstream 0.0000 0.0000 0.0000 FALSE wet
Upstream 1.0000 0.4448 0.7224 TRUE dry

Table 1: A summary of August 14th’s sensor’s thermal classification. The Upstream sensor is the only sensor to trigger a conflict flage due to the difference in warming and cooling scores. On this date with a dryness score of 0.7225, the sensor barely crossed the threshold and was classified as dry.

September 2nd, 2025 (Normal summer day)

Figure 12: Four-panel diagnostic plot for September 2nd, 2025. Temperatures ranged from 56–77°F with wind gusts up to 18 mph. The Midstream sensor was found displaced from its in-stream position during the September 2nd collection, producing a dry classification that reflects sensor displacement rather than true flow absence.

Dryness Scores — September 2nd, 2025 (Longitudinal Gradient)
Sensor warming_score cooling_score daily_score conflict_flag dryness_state
Air 0.4708 0.4586 0.4647 FALSE uncertain
Downstream 0.0000 0.0000 0.0000 FALSE wet
Midstream 1.0000 1.0000 1.0000 FALSE dry
Upstream 0.1766 0.0834 0.1300 FALSE wet

Table 2: A summary of September 2nd’s sensor’s thermal classification. The Midstream sensor was found displaced from its in-stream position during the September 9th collection visit, due to an external interference of a removed rebar which still had the sensor attached. Its dry classification on this day reflects sensor displacement rather than true flow absence. Downstream and Upstream confirmed wet conditions consistent with Senior Run’s established behavior.

December 2nd, 2025 (Precipitated winter day)

Figure 13: Four-panel diagnostic plot for December 2nd, 2025. Temperatures ranged from 28–40°F with 0.19 inches of precipitation and wind gusts of 14 mph. Morning rainfall suppressed the Air sensor’s warming signal, causing the Upstream sensor’s modest rise to appear disproportionately large by comparison, producing a conflict flag at that position.

Dryness Scores — December 2nd, 2025
Sensor warming_score cooling_score daily_score conflict_flag dryness_state
Air 1.0 1.0000 1.0000 FALSE dry
Downstream 0.0 0.0000 0.0000 FALSE wet
Midstream 0.2 0.0000 0.1000 FALSE wet
Upstream 1.0 0.0022 0.5011 TRUE uncertain

Table 3: A summary of December 2nd’s sensor’s thermal classification. Morning rainfall suppressed the Air sensor’s warming signal, causing the Upstream sensor’s modest temperature rise to appear disproportionately large by comparison which produced a conflict flag and uncertain classification. Downstream and Midstream classified wet with no flags, confirming persistent main channel flow.

December 10, 2025 (Normal winter day) Close-up

Figure 14: Four-panel diagnostic plot for December 10th, 2025. Temperatures ranged from 30–45°F with overcast skies and wind gusts of 13 mph. All three stream sensors classified wet with no conflict flags, displaying a clean longitudinal gradient. The Air sensor rose approximately 12°F above its morning minimum while stream sensors rose only 3–5°F. This is a clear demonstration of 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 dryness_state
Air 1.0000 1e+00 1.0000 FALSE dry
Downstream 0.0000 0e+00 0.0000 FALSE wet
Midstream 0.0000 0e+00 0.0000 FALSE wet
Upstream 0.0017 6e-04 0.0011 FALSE wet

Table 4: All three stream sensors classified wet with no conflict flags. Air scored 1.0 because its diurnal temperature swing remained responsive to atmospheric forcing while the stream sensors stayed thermally regulated by water.

Analysis

Over the course of the study, Senior Run maintained consistent surface flow at both its downstream and midstream locations, with both sensors categorized as wet on more than 90% of days during all periods. During the summer baseflow recession, the upstream location was dry more than half the time, and during the winter groundwater recharge, it recovered to almost zero dry days. The overall daily dryness heatmap shows this seasonal pattern, which is consistent with a mixed-permanence headwater stream in which the headwater portion reacts to seasonal variations in groundwater availability but the main channel maintains perennial flow. Physically, the Upstream sensor is positioned near the edge of surface water coverage within a saturated skunk cabbage community which played a role in amplifying its thermal responsiveness to the atmosphere. Senior Run demonstrates the defining thermal signature of a seasonally intermittent headwater stream.