NASA Space Apps 2026 // Trend Detective
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Case File #026-BD

The Bengal Water Paradox

Witness Reports Contradict: Is Bangladesh Drying Out or Drowning?
Witness A: Inland Northwest
CRACKED SOIL & DROUGHT

Local well reports and studies cite dropping water tables, dry suction tubewells in Rajshahi, and desertification risks during the Boro season.

Witness B: Northeast & Coast
EXTREME DELUGE & FLOODS

Regional papers report intensifying monsoon cloudbursts, severe flash flooding in Sylhet haors, and coastal sea-level inundation.

★ The Challenge: Cut through the noise and verify true long-term trends using NASA Earth observations.
Core Hypothesis

Where is Bangladesh's Water Going?[cite: 1]

Do rainfall and water-storage trends differ across divisions, and are those differences statistically significant?[cite: 1]

The Spatial Granularity Rule

  • National averages hide regional catastrophe by cancelling out opposite dynamics.
  • Dividing analysis across all 8 Administrative Divisions balances physical precision with sensor limits[cite: 1].
  • Northwest vs Northeast divergence under the same monsoon system.
8 Divisions Analyzed[cite: 1]
Rajshahi Rangpur Dhaka Mymensingh Sylhet Chattogram Khulna Barishal
Evidence Sources

Interrogating the Satellite Data[cite: 1]

Selecting two distinct NASA observational platforms[cite: 1]
1. GPM IMERG[cite: 1]
Precipitation Trends (2000–Present)[cite: 1]
  • Resolution: Fine spatial grid (~0.1°), ideal for regional maps[cite: 1].
  • Role: Measures incoming atmospheric water volume and extreme precipitation frequency[cite: 1].
2. GRACE / GRACE-FO[cite: 1]
Terrestrial Water Storage (TWS) (2002–Present)[cite: 1]
  • Resolution: Coarse spatial footprint (~300 km)[cite: 1].
  • Methodological Rigor: Aggregated strictly to division-level boundaries to prevent false localized claims[cite: 1].
  • Role: Directly measures sub-surface aquifer mass and total basin moisture change[cite: 1].
Statistical Engine

Filtering Noise from Climate Signal

Answering NASA's core challenge: proving statistical significance
STEP 1

STL Decomposition

Strips out the overwhelming annual monsoon waveform to uncover underlying secular trends.

STEP 2

Sen's Slope Estimator

Calculates robust, non-parametric physical rate of change (mm/yr for rain, cm/yr for water storage).

STEP 3

Mann-Kendall Test

Mathematically evaluates whether the trajectory is a real trend or a random anomaly (target: p < 0.05).

Verified: p < 0.05 Required for Policy Action
The Verdict

The Detective's Findings

The contradiction is resolved: Groundwater pumping vs. Rainfall volatility

Northwest (Rajshahi & Rangpur)

Δ Storage: -0.88 to -1.2 cm/yr
SIGNIFICANT: p < 0.01

Rainfall has remained relatively stable, but terrestrial storage is in continuous monotonic decline. Verdict: An irrigation-driven groundwater extraction crisis.

Northeast & Coast (Sylhet, Chattogram)

Rain Anomaly Spikes
SIGNIFICANT: p < 0.05

Precipitation is concentrating into higher-intensity bursts. Verdict: Flash flood exposure is surging despite fluctuating annual storage.

Interactive Product

HydroDetective: Bangladesh

A decision-support tool for water planners and agricultural authorities
Feature 1: Division-Level Query (Toggle GPM vs GRACE layers)[cite: 1]
Feature 2: Significance Mask (Hide divisions where p ≥ 0.05)
Feature 3: Bangla / English Policy Summaries
[ Interactive Dashboard Mockup: Dual-Axis Graph & Division Map Preview ]

Allows BWDB planners to pinpoint exactly where Boro rice irrigation must shift to drought-resilient crops.

Global Horizon

Scalable Across Every River Basin

Turning raw satellite data into verified environmental truth

Universal Architecture

While tested on the Bengal Basin, the analytical pipeline runs identically on any global watershed (e.g., Indus Basin, California Central Valley, Mekong Delta).

TEAM TREND DETECTIVES
AI Research • Data Analytics • Visual UI Design
NASA Space Apps 2026