Soil Property Maps for Colorado River Basin at 30-Meter Resolution

A 2026 compilation provides predictive soil property maps for the Colorado River Basin above Hoover Dam, generated using random forest models on environmental raster layers and field samples. The dataset includes estimates for soil pH, texture fractions, electrical conductivity, organic matter, and other properties at 7 depths, with model accuracy (R²) ranging from 0.20 to 0.76. More than 90% of the underlying soils data was sampled since the year 2000.

Use Cases

• Train random forest models to predict soil pH at different depths using environmental raster layers as features.
• Analyze spatial patterns of electrical conductivity (ec) and organic matter (om) across the basin for environmental monitoring.
• Estimate available water capacity (awc) and bulk density (dbovendry) to model hydrological processes and soil health.
• Map soil erodibility (kwfact) and depth to restrictive layer (resdept) for land management and erosion risk assessment.

Strengths

• Model performance is quantified, with a mean R² of 0.52 and specific properties like pH achieving R² > 0.6.
• Provides high-resolution 30-meter gridded predictions for 7 distinct soil depths (0, 5, 15, 30, 60, 100, and 200 cm).
• Includes relative prediction intervals for key properties, allowing users to evaluate uncertainty.
• Over 90% of the foundational field sample data is from the year 2000 or later, ensuring modern relevance.

Limitations

• Model performance is poor for very fine sand estimates and predictions at the 200 cm depth, with R² values between 0.2 and 0.4.
• Sample size for building the 200 cm depth models was explicitly noted as too low for reliable modeling.
• The dataset incorporates some older soil samples alongside the post-2000 data, which may introduce temporal inconsistencies.

Provenance

Source

Department of the Interior

Collection Method

Random forest models applied to relate environmental raster layers (soil forming factors) with field samples for predictive mapping.

Time Range

Primarily post-2000 field samples, with some older samples included.

Freshness

Last updated in January 2026.

Geography

Colorado River Basin above Hoover Dam, covering parts of Arizona and Colorado.