Rainfall vs Evaporation

Overview

Rainfall vs evaporation charts compare two opposing water cycle processes over time. This visualization is crucial for understanding water balance, drought conditions, and agricultural water availability.

When to use

Climate and hydrology analysis
Agricultural water management
Drought monitoring and prediction
Water resource planning
Ecosystem health assessment
Irrigation scheduling

Not ideal

When only one metric matters
Short-term (daily) analysis (too volatile)
Without context about region or measurement methodology

Key variations

Dual Y-axes for different scales
Net water balance (rainfall - evaporation) as third line
Cumulative vs period values
Monthly vs annual aggregation
Add reference lines for critical thresholds

Use cases

Agricultural planning: crop water requirements
Reservoir management: predict water levels
Climate research: regional water cycle patterns
Environmental monitoring: wetland sustainability
Urban planning: stormwater and irrigation systems

Data (CSV)

time,value,series
7/22 22:00,0.1,Evaporation
7/22 22:00,0,Rainfall
7/25 12:00,0.2,Evaporation
7/25 12:00,0.2,Rainfall
7/28 18:00,0.5,Evaporation
7/28 18:00,3.8,Rainfall
8/1 06:00,3.0,Evaporation
8/1 06:00,0,Rainfall
8/2 18:00,10,Evaporation
8/2 18:00,0.4,Rainfall
8/3 02:00,150,Evaporation
8/3 02:00,0.3,Rainfall
8/3 10:00,220,Evaporation
8/3 10:00,0.6,Rainfall
8/3 18:00,80,Evaporation
8/3 18:00,0.1,Rainfall
8/4 06:00,20,Evaporation
8/4 06:00,0,Rainfall
8/9 10:00,0.4,Evaporation
8/9 10:00,0,Rainfall
8/12 12:00,0.7,Evaporation
8/12 12:00,0.1,Rainfall
8/15 06:00,5.0,Evaporation
8/15 06:00,9.1,Rainfall
8/18 06:00,18,Evaporation
8/18 06:00,1.2,Rainfall
8/21 02:00,245,Evaporation
8/21 02:00,7.9,Rainfall
8/22 18:00,120,Evaporation
8/22 18:00,0.8,Rainfall
8/24 12:00,45,Evaporation
8/24 12:00,0.3,Rainfall
8/26 22:00,20,Evaporation
8/26 22:00,0.2,Rainfall
8/29 08:00,12,Evaporation
8/29 08:00,0.5,Rainfall
9/1 18:00,30,Evaporation
9/1 18:00,2.1,Rainfall
9/4 12:00,6,Evaporation
9/4 12:00,0.1,Rainfall
9/7 14:00,0.3,Evaporation
9/7 14:00,0,Rainfall

Performance tips

Use monthly or weekly aggregation for readability
Consider area charts to emphasize magnitude
Add cumulative lines for total annual comparison
Highlight deficit periods (evaporation > rainfall)

FAQ

What does it mean when evaporation exceeds rainfall? This indicates a water deficit period, potentially leading to drought conditions if prolonged.

Should I use dual Y-axes? Typically no—rainfall and evaporation use the same units (mm). Use a single axis unless showing net balance requires different scale.

How to show cumulative totals? Add a secondary chart or use a dual-axis approach with period values on left and cumulative on right.

What about potential evapotranspiration (PET)? PET is theoretical max evaporation. If comparing PET to actual rainfall, clearly label which you're showing.

How to account for different measurement methods? Add methodology notes in subtitle or footnote. Pan evaporation differs from computed PET.

Can I show multiple years? Yes, use small multiples (one chart per year) or overlay with different colors/styles. Annual comparison reveals climate trends.

Example

Guide