What Is It? A dual-axis temporal visualization showing both the volume of data collected (measurements per month) and the number of active monitoring points (wells reporting). This βsmall multiplesβ approach reveals patterns in data collection effort, equipment failures, and network expansion/contraction over time.
Why Does It Matter? Groundwater monitoring networks evolveβwells get added, sensors fail, budgets fluctuate. Coverage gaps create blind spots in analysis: if the network went offline for 3 months in 2019, any trend analysis spanning that period is suspect. Knowing when and where coverage dropped helps interpret historical patterns and identify systematic issues (e.g., βEvery winter we lose 30% of wells to freezingβ).
How Does It Work?
The chart uses two y-axes to show related metrics: - Left axis (bars): Total measurements collected that month - Right axis (line): Number of unique wells that reported at least once
What Will You See? Monthly bar chart (blue) showing measurement counts overlaid with line plot (orange) tracking active well count. Synchronized dips in both indicate network-wide issues; bars dropping while line stays high suggests reduced sampling frequency.
How to Interpret Patterns:
| Healthy baseline |
High, consistent |
Stable |
Normal operations |
Continue monitoring |
| Synchronized drop |
β¬οΈ |
β¬οΈ |
Network-wide issue (power, budget, weather) |
Investigate infrastructure |
| Bars drop, line stable |
β¬οΈ |
β |
Reduced sampling frequency (budget cuts?) |
Review monitoring protocol |
| Bars stable, line drops |
β |
β¬οΈ |
Wells going offline permanently |
Plan replacements |
| Gradual increase |
β¬οΈ |
β¬οΈ |
Network expansion (good!) |
Document new wells |
| Seasonal oscillation |
β¬οΈβ¬οΈ |
β |
Seasonal access issues (winter freeze) |
Expected, plan around it |
Specific Interpretation Examples:
Example 1: Budget Cut Impact - Bars drop 60% but line only drops 10% - Interpretation: Still monitoring most wells, but less frequently (monthly instead of weekly) - Impact: Long-term trends still visible, but canβt detect short-term anomalies - Management decision: Acceptable if budget constrained; prioritize high-value wells for more frequent sampling
Example 2: Equipment Failure - Sudden 40% drop in both bars and line over 2 months - Interpretation: Telemetry system failed, losing data from entire region - Impact: Blind spot in spatial coverage, missing recharge events - Management decision: Emergency equipment repair/replacement needed
Example 3: Winter Freeze Pattern - Regular drops in January-February every year - Interpretation: Expected pattern in cold climates (sensors freeze, access difficult) - Impact: Seasonal data gaps, donβt mistake for equipment failure - Management decision: Install freeze-resistant sensors or accept winter gaps
Coverage Quality Thresholds:
| Excellent |
>1500/month |
>80% of wells |
All analyses valid |
| Good |
1000-1500 |
60-80% |
Most analyses valid, some spatial gaps |
| Marginal |
500-1000 |
40-60% |
Trends visible, detailed analysis risky |
| Poor |
<500 |
<40% |
Major blind spots, donβt trust analyses |
Historical Context Matters:
When interpreting current data, check this panel first: - βWater levels dropped in 2020β β Check coverage. If 50% of wells offline, trend may be artifact - βSpring 2018 shows low rechargeβ β Check coverage. If measurements sparse, conclusion uncertain - βWell #47 is anomalousβ β Check if other nearby wells have data same period
Management Use:
- Budget planning: Show council βWe lost 40% coverage in 2019 due to cuts. Do we want to repeat that?β
- Equipment investment: βThree sudden drops suggest telemetry is aging. Time to upgrade?β
- Performance reporting: βWe maintained 75% coverage despite 20% budget cut.β