How it works
Every chart on this dashboard measures one piece of the same water cycle. This page explains how those pieces connect, starting from rain and ending at groundwater.
The journey of water
Precipitation falls
Rain is the system's input. A wet month refills the system from top to bottom; a dry month starves every downstream variable.
tpPart returns to the atmosphere
Plants and bare soil release water back as vapour. When evapotranspiration is high — usually hot, dry months — less water is available to infiltrate.
epevThe rest enters the soil
Water moves downward through two layers. The root zone (shallow) fills first; only when it is already wet does surplus water keep moving deeper into the soil profile.
sm_rsm_pSome of it recharges the aquifer
Water that passes through the full soil column reaches the saturated zone and becomes groundwater recharge. This is estimated two ways: from the GRACE satellite signal and from the water balance equation, providing a cross-check.
recharge_dgwsrecharge_wbGroundwater storage responds
The aquifer integrates everything above. Storage rises after sustained wet and recharge-positive periods; it falls during droughts or heavy extraction. Because it integrates over time, groundwater anomalies often lag precipitation anomalies by months.
gwstwsThe water balance
P = ET + Q + R ± ΔS
Water balance equation
- P
- Precipitation Rain and snow — the main water input to the basin.
- ET
- Evapotranspiration Water returned to the atmosphere by evaporation and plant transpiration.
- Q
- Runoff Water that flows overland to rivers and streams.
- R
- Recharge Water that infiltrates deep enough to replenish the aquifer.
- ΔS
- Change in storage Net gain or loss in groundwater and soil water held in the basin.
Reading the charts
Solid line — observed value
The main line shows the monthly value for the selected cell or area. For area selections it is the median across all grid cells inside the selection.
Shaded band — climatology or spatial spread
For cell selections the band shows the 2004–2020 monthly normal range (p10–p90 of the historical distribution for that calendar month). For area selections it shows the spatial spread across grid cells in the selected region — a wide band means cells inside the area disagree strongly.
Dashed vertical line — selected month
The line marks the month you have chosen on the timeline. Moving the timeline moves this marker across all charts simultaneously, so you can compare the same moment across all variables.
Anomaly vs raw value
Some charts show raw values (e.g. mm of groundwater storage). Others show anomalies — the departure from the 2004–2020 average for that calendar month. A negative anomaly means "below what is normal for this time of year", not necessarily below zero.
Variable reference
| Variable | What it measures |
|---|---|
tp | Precipitation |
e | Evapotranspiration (actual) |
pev | Potential evapotranspiration |
cwd | Climate water balance (P − PET) |
t2m | Near-surface air temperature |
sm_r | Root-zone soil moisture |
sm_p | Profile soil moisture (deep) |
recharge_dgws | Groundwater gain / loss (GRACE-based) |
recharge_wb | Recharge estimate (water balance) |
gws | Groundwater storage |
tws | Total water storage |