pyGWRetrieval 0.1.0
A Python package for retrieving USGS groundwater level data
Requires Python: >=3.8
Keywords: groundwater, USGS, hydrology, water-resources, data-retrieval, NWIS, geospatial, time-series

# pyGWRetrieval

A Python package for retrieving and analyzing USGS groundwater level data.

[![GitHub Pages](https://img.shields.io/badge/docs-GitHub%20Pages-blue?logo=github)](https://montimaj.github.io/pyGWRetrieval/)
[![Python Version](https://img.shields.io/badge/python-3.9%2B-blue.svg)](https://www.python.org/downloads/)
[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)

## Overview

**pyGWRetrieval** simplifies the process of downloading daily groundwater level data from the USGS National Water Information System (NWIS). It supports various spatial inputs including:

- **Zip codes** with customizable buffer distances
- **GeoJSON files** for custom areas of interest
- **Shapefiles** including state boundaries or groundwater basins
- **Point vectors** with buffer capabilities
- **Polygon features** for direct spatial queries

## Features

- 🌍 **Flexible Spatial Inputs**: Query by zip code, GeoJSON, shapefile, or specific site numbers
- � **Multiple Data Sources**: Retrieve from gwlevels, daily values, or instantaneous values
- 📊 **Temporal Aggregation**: Aggregate data to monthly, annual, growing season, or custom periods
- 📈 **Visualization**: Built-in plotting for time series analysis
- 💾 **Multiple Export Formats**: Save data as CSV or Parquet files
- 🔧 **Trend Analysis**: Calculate linear trends for water level changes
- ⚡ **Parallel Processing**: Dask-powered parallel processing for large datasets

## USGS Data Sources

pyGWRetrieval supports three USGS NWIS data sources for groundwater levels:

| Source | Description | Typical Use Case |
|--------|-------------|------------------|
| `gwlevels` | **Field groundwater-level measurements** - Discrete manual measurements taken during field visits. Most accurate but infrequent. | Long-term trend analysis, calibration |
| `dv` | **Daily values** - Daily statistical summaries (mean, min, max) computed from continuous sensors. | Regular monitoring, daily patterns |
| `iv` | **Instantaneous values** - Current/historical observations at 15-60 minute intervals from continuous sensors. | High-resolution analysis, recent conditions |

### Selecting Data Sources

```python
from pyGWRetrieval import GroundwaterRetrieval

# Default: gwlevels only (backward compatible)
gw = GroundwaterRetrieval(start_date='2020-01-01')
data = gw.get_data_by_zipcode('89701', buffer_miles=10)

# All available sources
gw_all = GroundwaterRetrieval(
    start_date='2020-01-01',
    data_sources='all'  # gwlevels + dv + iv
)

# Specific sources
gw_daily = GroundwaterRetrieval(
    start_date='2020-01-01',
    data_sources=['gwlevels', 'dv']  # Field measurements + daily values
)

# Single source
gw_instant = GroundwaterRetrieval(
    start_date='2020-01-01',
    data_sources='iv'  # Instantaneous values only
)
```

The output data includes a `data_source` column to identify which source each record came from.

> **Note on Data Aggregation**: All three data types (`gwlevels`, `dv`, `iv`) are stored as-is after download without any aggregation or transformation. Daily values (`dv`) are pre-computed by USGS, and instantaneous values (`iv`) retain their original high-frequency resolution (typically 15-60 minute intervals). If you need to aggregate `iv` data to daily or other frequencies, use the `TemporalAggregator` class from the `temporal` module.

## Installation

### Using pip

```bash
pip install pyGWRetrieval
```

### From source

```bash
git clone https://github.com/montimaj/pyGWRetrieval.git
cd pyGWRetrieval
pip install -e .
```

### With optional dependencies

```bash
# For enhanced visualization
pip install pyGWRetrieval[viz]

# For distributed computing (multi-node parallelism)
pip install pyGWRetrieval[distributed]

# For development
pip install pyGWRetrieval[dev]

# For documentation
pip install pyGWRetrieval[docs]

# All optional dependencies
pip install pyGWRetrieval[all]
```

## Project Structure

```
pyGWRetrieval/
├── pyGWRetrieval/           # Main package
│   ├── __init__.py          # Package initialization and exports
│   ├── retrieval.py         # Core GroundwaterRetrieval class
│   ├── spatial.py           # Spatial utilities (zip codes, geometries, buffers)
│   ├── temporal.py          # Temporal aggregation and trend analysis
│   ├── visualization.py     # Plotting and visualization tools
│   ├── parallel.py          # Dask-based parallel processing
│   ├── cli.py               # Command-line interface
│   └── utils.py             # Helper functions and utilities
├── docs/                    # Documentation (Sphinx)
│   ├── index.md             # Documentation home
│   ├── quickstart.md        # Getting started guide
│   ├── api_reference.md     # API documentation
│   └── cli.md               # CLI documentation
├── examples/                # Example scripts
│   ├── basic_usage.py       # Simple usage examples
│   ├── full_workflow_csv_zipcodes.py  # Complete workflow
│   ├── multi_source_example.py        # Multi-source retrieval
│   ├── temporal_analysis.py           # Temporal aggregation
│   └── advanced_spatial.py            # Spatial queries
├── tests/                   # Unit tests
├── pyproject.toml           # Package configuration
├── setup.py                 # Setup script
├── requirements.txt         # Dependencies
├── LICENSE                  # MIT License
└── README.md                # This file
```

## Quick Start

### Basic Usage

```python
from pyGWRetrieval import GroundwaterRetrieval

# Initialize with date range
gw = GroundwaterRetrieval(
    start_date='2010-01-01',
    end_date='2023-12-31'
)

# Get data by zip code with 10-mile buffer
data = gw.get_data_by_zipcode('89701', buffer_miles=10)

# Save to CSV
gw.to_csv('groundwater_data.csv')
```

### Using Multiple Zip Codes from CSV

```python
from pyGWRetrieval import GroundwaterRetrieval

gw = GroundwaterRetrieval()

# Read zip codes from CSV file - parallel processing is enabled by default
data = gw.get_data_by_zipcodes_csv(
    'locations.csv',
    zipcode_column='zip',  # Name of column with zip codes
    buffer_miles=10,
    parallel=True,         # Enable parallel processing (default)
    n_workers=4            # Optional: specify number of workers
)

# Results include 'source_zipcode' column to track origin
print(data['source_zipcode'].value_counts())

# Save data to separate files per zip code
saved_files = gw.save_data_per_zipcode('output_by_zipcode/', file_format='csv')
for zipcode, filepath in saved_files.items():
    print(f"Saved {zipcode} to {filepath}")
```

### Using Shapefiles

```python
from pyGWRetrieval import GroundwaterRetrieval

gw = GroundwaterRetrieval()

# Get data within a polygon (e.g., basin boundary)
data = gw.get_data_by_shapefile('my_basin.shp')

# For point shapefiles, specify a buffer
data = gw.get_data_by_shapefile('well_locations.shp', buffer_miles=5)
```

### Using GeoJSON

```python
from pyGWRetrieval import GroundwaterRetrieval

gw = GroundwaterRetrieval(start_date='2020-01-01')

# Get data within GeoJSON polygons
data = gw.get_data_by_geojson('study_area.geojson')

# Save as Parquet
gw.to_parquet('groundwater_data.parquet')
```

### Temporal Aggregation

```python
from pyGWRetrieval import GroundwaterRetrieval, TemporalAggregator

# Get raw data
gw = GroundwaterRetrieval()
data = gw.get_data_by_zipcode('89701', buffer_miles=20)

# Aggregate temporally
aggregator = TemporalAggregator(data)

# Monthly means
monthly = aggregator.to_monthly(agg_func='mean')

# Annual medians
annual = aggregator.to_annual(agg_func='median')

# Growing season (April-September)
growing = aggregator.to_growing_season(start_month=4, end_month=9)

# Water year
water_year = aggregator.to_annual(water_year=True)

# Custom period (e.g., summer months)
summer = aggregator.to_custom_period(months=[6, 7, 8], period_name='summer')
```

### Visualization

```python
from pyGWRetrieval import GroundwaterRetrieval, GroundwaterPlotter
import matplotlib.pyplot as plt

# Get data
gw = GroundwaterRetrieval()
data = gw.get_data_by_zipcode('89701', buffer_miles=15)

# Create plotter
plotter = GroundwaterPlotter(data)

# Time series for all wells
fig = plotter.plot_time_series()
plt.savefig('time_series.png')

# Single well detailed plot
fig = plotter.plot_single_well('390000119000001')
plt.savefig('single_well.png')

# Monthly boxplot
fig = plotter.plot_monthly_boxplot()
plt.savefig('monthly_boxplot.png')

# Annual summary
fig = plotter.plot_annual_summary()
plt.savefig('annual_summary.png')
```

### Spatial Map Visualization

Create maps showing wells colored by water level with automatic zoom:

```python
from pyGWRetrieval import GroundwaterRetrieval, plot_wells_map, create_comparison_map
import matplotlib.pyplot as plt

# Get data from multiple zip codes
gw = GroundwaterRetrieval()
data = gw.get_data_by_zipcodes_csv('locations.csv', zipcode_column='zip', buffer_miles=20)

# Create a spatial map with auto-zoom
# - Local extent (<20 mi): detailed zoom
# - Regional extent (<100 mi): wider view
# - State extent (<500 mi): state-level view
# - National extent (>1500 mi): continental view
fig = plot_wells_map(
    data,
    agg_func='mean',  # Show mean water level per well
    title='Groundwater Wells (ft below surface)',
    cmap='RdYlBu_r',  # Red=deep water, Blue=shallow
    add_basemap=True,  # Add OpenStreetMap-style basemap
    group_by_column='source_zipcode'  # Label by zip code
)
plt.savefig('wells_map.png', dpi=300)

# Create a 4-panel comparison map (mean, min, max, record count)
fig = create_comparison_map(data, figsize=(18, 12))
plt.savefig('comparison_map.png', dpi=300)
```

### Parallel Processing

pyGWRetrieval uses Dask for parallel processing of large datasets:

```python
from pyGWRetrieval import GroundwaterRetrieval, check_dask_available, get_parallel_config

# Check if parallel processing is available
print(f"Dask available: {check_dask_available()}")
print(f"Config: {get_parallel_config()}")

# Parallel processing is enabled by default for multi-zipcode queries
gw = GroundwaterRetrieval(start_date='1970-01-01')
data = gw.get_data_by_zipcodes_csv(
    'locations.csv',
    zipcode_column='zip',
    parallel=True,           # Default
    n_workers=4,             # Number of parallel workers
    scheduler='threads'      # 'threads', 'processes', or 'synchronous'
)

# For distributed computing across multiple machines
from pyGWRetrieval import get_dask_client

client = get_dask_client(n_workers=8)  # Creates local cluster
# Dashboard available at client.dashboard_link
```

## Command Line Interface (CLI)

pyGWRetrieval provides a full-featured CLI for all operations.

### Installation

After installing the package, the `pygwretrieval` command is available:

```bash
pygwretrieval --help
```

### Retrieve Data

```bash
# By zip code with buffer (default: gwlevels only)
pygwretrieval retrieve --zipcode 89701 --buffer 10 --output data.csv

# Retrieve from all USGS data sources (gwlevels, dv, iv)
pygwretrieval retrieve --zipcode 89701 --buffer 10 --data-sources all --output data.csv

# Retrieve from specific sources
pygwretrieval retrieve --zipcode 89701 --data-sources gwlevels dv --output data.csv

# From CSV file with multiple zip codes (parallel processing)
pygwretrieval retrieve --csv locations.csv --zipcode-column zip --parallel --output data.csv

# Multi-source retrieval from CSV
pygwretrieval retrieve --csv locations.csv --zipcode-column zip --data-sources all --parallel --output data.csv

# Save separate files per zip code
pygwretrieval retrieve --csv locations.csv --zipcode-column zip --save-per-zipcode --per-zipcode-dir output/

# From shapefile
pygwretrieval retrieve --shapefile basin.shp --buffer 5 --output basin_data.csv

# From GeoJSON
pygwretrieval retrieve --geojson study_area.geojson --output area_data.csv

# By state
pygwretrieval retrieve --state NV --output nevada_data.csv

# Specific sites
pygwretrieval retrieve --sites 390000119000001 390000119000002 --output sites_data.csv

# With date range
pygwretrieval retrieve --zipcode 89701 --start-date 2010-01-01 --end-date 2023-12-31 --output data.csv

# Save well locations as GeoJSON
pygwretrieval retrieve --zipcode 89701 --buffer 15 --output data.csv --wells-output wells.geojson
```

### Aggregate Data

```bash
# Monthly aggregation
pygwretrieval aggregate --input data.csv --period monthly --output monthly.csv

# Annual aggregation
pygwretrieval aggregate --input data.csv --period annual --agg-func mean --output annual.csv

# Water year aggregation
pygwretrieval aggregate --input data.csv --period water-year --output water_year.csv

# Growing season (April-September)
pygwretrieval aggregate --input data.csv --period growing-season --start-month 4 --end-month 9 --output growing.csv

# Custom period with median
pygwretrieval aggregate --input data.csv --period custom --start-month 6 --end-month 8 --agg-func median --output summer.csv
```

### Calculate Statistics and Trends

```bash
# Both statistics and trends
pygwretrieval stats --input data.csv --output analysis

# Statistics only
pygwretrieval stats --input data.csv --output stats --type statistics

# Trends with parallel processing
pygwretrieval stats --input data.csv --output trends --type trends --parallel
```

### Create Visualizations

```bash
# Time series plot
pygwretrieval plot --input data.csv --type timeseries --output timeseries.png

# Single well detailed plot with trend
pygwretrieval plot --input data.csv --type single-well --wells 390000119000001 --show-trend --output well.png

# Monthly boxplot
pygwretrieval plot --input data.csv --type boxplot --output boxplot.png

# Annual summary
pygwretrieval plot --input data.csv --type annual --output annual.png

# Custom figure size and DPI
pygwretrieval plot --input data.csv --type timeseries --figsize 14 10 --dpi 300 --output plot.png
```

### Create Spatial Maps

```bash
# Basic map with basemap
pygwretrieval map --input data.csv --output wells_map.png --basemap

# Map with custom colormap and grouping
pygwretrieval map --input data.csv --output map.png --basemap --cmap viridis --group-by source_zipcode

# Different basemap provider
pygwretrieval map --input data.csv --output map.png --basemap --basemap-source Esri.WorldImagery

# Comparison map (4 panels: mean, count, min, max)
pygwretrieval map --input data.csv --output comparison.png --comparison --basemap
```

### Get Data Information

```bash
# Basic info
pygwretrieval info --input data.csv

# Detailed statistics
pygwretrieval info --input data.csv --detailed
```

### Global Options

```bash
# Verbose output
pygwretrieval -v retrieve --zipcode 89701 --output data.csv

# Quiet mode (errors only)
pygwretrieval -q retrieve --zipcode 89701 --output data.csv

# Version
pygwretrieval --version
```

## API Reference

### Core Classes

#### `GroundwaterRetrieval`

Main class for data retrieval from USGS NWIS.

```python
GroundwaterRetrieval(start_date='1900-01-01', end_date=None, data_sources='gwlevels')
```

**Parameters:**
- `start_date` (str): Start date in 'YYYY-MM-DD' format (default: '1900-01-01')
- `end_date` (str): End date (default: today)
- `data_sources` (str | List): Data sources to retrieve:
  - `'gwlevels'` (default): Field measurements
  - `'dv'`: Daily values
  - `'iv'`: Instantaneous values
  - `'all'`: All sources
  - `['gwlevels', 'dv']`: List of specific sources

**Methods:**
- `get_data_by_zipcode(zipcode, buffer_miles, country)` - Query by zip code
- `get_data_by_zipcodes_csv(filepath, zipcode_column, buffer_miles)` - Query multiple zip codes from CSV
- `get_data_by_geojson(filepath, buffer_miles, layer)` - Query using GeoJSON
- `get_data_by_shapefile(filepath, buffer_miles)` - Query using shapefile
- `get_data_by_state(state_code)` - Query entire state
- `get_data_by_sites(site_numbers)` - Query specific sites
- `to_csv(filepath)` - Export to CSV
- `to_parquet(filepath)` - Export to Parquet
- `save_data_per_zipcode(output_dir, file_format, prefix)` - Save data per zip code

#### `TemporalAggregator`

Class for temporal aggregation of groundwater data.

```python
TemporalAggregator(data, date_column='lev_dt', value_column='lev_va', site_column='site_no')
```

**Methods:**
- `to_monthly(agg_func, include_count)` - Monthly aggregation
- `to_annual(agg_func, water_year)` - Annual aggregation
- `to_growing_season(start_month, end_month, region)` - Growing season aggregation
- `to_custom_period(months, period_name)` - Custom period aggregation
- `to_weekly(agg_func)` - Weekly aggregation
- `resample(freq, agg_func)` - Pandas resample
- `calculate_statistics(groupby)` - Comprehensive statistics
- `get_trends(period)` - Linear trend analysis

#### `GroundwaterPlotter`

Class for visualization of groundwater data.

```python
GroundwaterPlotter(data, date_column='lev_dt', value_column='lev_va', site_column='site_no')
```

**Methods:**
- `plot_time_series(wells, figsize, title)` - Time series plots
- `plot_single_well(site_no, show_trend, show_stats)` - Detailed single well plot
- `plot_comparison(wells, normalize)` - Multi-well comparison
- `plot_monthly_boxplot(wells)` - Monthly distribution
- `plot_annual_summary(wells, agg_func)` - Annual statistics
- `plot_heatmap(well, cmap)` - Year-month heatmap
- `plot_spatial_distribution(wells_gdf)` - Spatial map

### Utility Functions

```python
from pyGWRetrieval import (
    save_to_csv,
    save_to_parquet,
    validate_date_range,
    setup_logging,
)

# Configure logging
setup_logging(level=logging.DEBUG, log_file='pyGWRetrieval.log')
```

## Data Sources

This package retrieves data from the **USGS National Water Information System (NWIS)** using the [dataretrieval-python](https://github.com/DOI-USGS/dataretrieval-python) library.

### Available Data Sources

| Source | API Function | Description | Use Case |
|--------|-------------|-------------|----------|
| `gwlevels` | `get_gwlevels()` | **Field measurements** - Discrete manual readings during field visits | Long-term trends, calibration |
| `dv` | `get_dv()` | **Daily values** - Daily statistical summaries from continuous sensors | Regular monitoring |
| `iv` | `get_iv()` | **Instantaneous values** - High-frequency (15-60 min) sensor data | Real-time analysis |

### USGS Parameter Codes

The following parameter codes are used for groundwater levels:
- **72019**: Depth to water level, feet below land surface
- **72020**: Elevation above NGVD 1929, feet
- **62610**: Groundwater level above NGVD 1929, feet
- **62611**: Groundwater level above NAVD 1988, feet

**Site Type**: GW (Groundwater)

### Data Columns and Units

The package retrieves groundwater level data with the following columns:

| Column | Description | Units |
|--------|-------------|-------|
| `site_no` | USGS site identification number | - |
| `lev_dt` | Date of water level measurement | Date (YYYY-MM-DD) |
| `lev_tm` | Time of measurement | Time (HH:MM) |
| `lev_va` | Water level value | **Feet below land surface** |
| `lev_acy_cd` | Water level accuracy code | - |
| `lev_src_cd` | Source of water level data | - |
| `lev_meth_cd` | Method of measurement code | - |
| `lev_status_cd` | Status of the site at time of measurement | - |
| `station_nm` | Station name (merged from site info) | - |
| `dec_lat_va` | Decimal latitude | Degrees |
| `dec_long_va` | Decimal longitude | Degrees |
| `source_zipcode` | Source zip code (for CSV queries) | - |

### USGS Parameter Codes

| Code | Description | Units |
|------|-------------|-------|
| `72019` | Depth to water level below land surface | Feet |
| `72020` | Elevation above NGVD 1929 | Feet |
| `62610` | Groundwater level above NGVD 1929 | Feet |
| `62611` | Groundwater level above NAVD 1988 | Feet |

> **Note**: The primary measurement `lev_va` represents depth to water in **feet below land surface**. Lower values indicate a shallower water table, while higher values indicate deeper groundwater.

## Requirements

- Python ≥ 3.8
- dataretrieval ≥ 1.0.0
- pandas ≥ 1.3.0
- geopandas ≥ 0.10.0
- shapely ≥ 1.8.0
- pyproj ≥ 3.0.0
- pgeocode ≥ 0.3.0
- matplotlib ≥ 3.4.0
- numpy ≥ 1.20.0

### Optional Dependencies

- seaborn (enhanced visualizations)
- contextily (basemaps for spatial plots)
- pyarrow (Parquet support)
- scipy (trend analysis)

### Storage Requirements

Storage requirements vary based on the number of zip codes, buffer distance, and data sources queried. Below are example estimates based on the `full_workflow_csv_zipcodes.py` example (99 zip codes, 25-mile buffer, gwlevels source, ~8M records):

| Component | Size | Description |
|-----------|------|-------------|
| Combined Parquet | ~80 MB | All retrieved groundwater data |
| Per-zipcode data | ~130 MB | Individual parquet files per zip code |
| Wells GeoJSON | ~25 MB | Well locations with metadata |
| Aggregated CSVs | ~27 MB | Monthly and annual aggregations |
| Visualization plots | ~15 MB | 15 PNG figures at 300 DPI |
| Analysis CSVs | ~2 MB | Trends, statistics, projections |
| **Total** | **~275 MB** | Complete workflow output |

**Scaling estimates:**
- ~3 MB per 1,000 wells retrieved
- ~10 KB per groundwater measurement record (Parquet format)
- Plot sizes: ~0.5-1.5 MB each at 300 DPI

> **Tip**: Use Parquet format (default) for efficient storage. Parquet files are ~60% smaller than equivalent CSV files and load significantly faster.

## Examples

The `examples/` directory contains several example scripts:

- **`basic_usage.py`** - Basic data retrieval and visualization
- **`temporal_analysis.py`** - Temporal aggregation and trend analysis
- **`advanced_spatial.py`** - Advanced spatial queries
- **`full_workflow_csv_zipcodes.py`** - Complete end-to-end workflow

### Full Workflow Example

The `full_workflow_csv_zipcodes.py` demonstrates a complete pipeline:

```python
from pyGWRetrieval import GroundwaterRetrieval, TemporalAggregator, GroundwaterPlotter

# 1. Read zip codes from CSV and download data from ALL USGS sources
gw = GroundwaterRetrieval(
    start_date='1970-01-01',
    data_sources='all'  # gwlevels + dv + iv
)
data = gw.get_data_by_zipcodes_csv(
    'locations.csv',
    zipcode_column='ZipCode',
    buffer_miles=100
)

# Data includes 'data_source' column identifying record origin
print(data.groupby('data_source').size())

# 2. Save combined and per-zipcode data
gw.to_csv('all_data.csv')
saved = gw.save_data_per_zipcode('output/', file_format='csv')

# 3. Temporal aggregation
aggregator = TemporalAggregator(data)
monthly = aggregator.to_monthly()
annual = aggregator.to_annual()

# 4. Visualization
plotter = GroundwaterPlotter(data)
fig = plotter.plot_time_series()
```

This workflow:
- Processes multiple zip codes from a CSV file
- Downloads historical groundwater data (1970-present)
- Saves data both combined and per zip code
- Performs monthly and annual aggregations
- Creates time series, boxplot, and comparison visualizations

## Case Study: Regional Groundwater Analysis of 9 U.S. Metropolitan Areas

The `full_workflow_csv_zipcodes.py` example demonstrates a comprehensive regional groundwater analysis across nine major U.S. Metropolitan Statistical Areas (MSAs): New York, Miami, Washington DC, Houston, Boston, Philadelphia, San Francisco, Chicago, and Dallas.

### Study Overview

| Metric | Value |
|--------|-------|
| Total Records | 7,995,927 |
| Monitoring Wells | 33,018 |
| Temporal Coverage | 1970-2025 (55 years) |
| Metropolitan Areas | 9 |
| Zip Codes Analyzed | 99 |
| Visualizations Generated | 15 figures |

### Key Findings

- **Dallas** shows remarkable groundwater recovery (+10.6 ft/year rising trend)
- **Washington DC** is the only region with significant declining trend (+1.1 ft/year deepening)
- **Miami** demonstrates the most stable groundwater conditions (lowest variability)
- **5 of 9 regions** show statistically significant long-term trends (p < 0.05)

### Generated Analyses

The workflow produces 15 publication-ready visualizations:

1. **Regional Trends** - Trend analysis by MSA
2. **Data Quality** - Coverage and density metrics
3. **Distributions** - Water level statistical distributions
4. **Temporal Patterns** - Decadal and seasonal patterns
5. **Monthly/Annual Boxplots** - Seasonal and inter-annual variability
6. **Correlation & Clustering** - Inter-regional relationships
7. **Extreme Events** - Drought and anomaly analysis
8. **Rate of Change** - Trend acceleration analysis
9. **Geographic Patterns** - Coastal vs. inland comparisons
10. **Change Point Detection** - Regime shift identification
11. **Sustainability Index** - Risk assessment (0-100 scale)
12. **Future Projections** - 5, 10, 20-year water level forecasts
13. **Comprehensive Statistics** - Publication-ready summary tables

### Output Files

- **Data**: Parquet files (~275 MB total), GeoJSON well locations
- **Analysis**: CSV files with trends, projections, sustainability metrics
- **Report**: Auto-generated markdown report (`ANALYSIS_REPORT.md`)
- **Visualizations**: 15 PNG figures at 300 DPI

See [examples/output/ANALYSIS_REPORT.md](examples/output/ANALYSIS_REPORT.md) for the complete analysis report.

## Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

1. Fork the repository
2. Create your feature branch (`git checkout -b feature/AmazingFeature`)
3. Commit your changes (`git commit -m 'Add some AmazingFeature'`)
4. Push to the branch (`git push origin feature/AmazingFeature`)
5. Open a Pull Request

## License

This project is licensed under the MIT License - see the [LICENSE](LICENSE) file for details.

## Citation

If you use this package in your research, please cite:

```bibtex
@software{pyGWRetrieval,
  author = {Sayantan Majumdar},
  title = {pyGWRetrieval: Scalable Retrieval and Analysis of USGS Groundwater Level Data},
  year = {2026},
  url = {https://github.com/montimaj/pyGWRetrieval}
}
```

## Acknowledgments

- [USGS](https://www.usgs.gov/) for providing groundwater data through NWIS
- [dataretrieval-python](https://github.com/DOI-USGS/dataretrieval-python) for the NWIS API interface