Lari et al. (2025) Quantifying sediment yield and discharge fluctuations using the GeoWEPP in response to soil and water conservation practices

Identification

• Journal: International Journal of Sediment Research
• Year: 2025
• Date: 2025-11-28
• Authors: Masoumeh Lari, Aliakbar Nazari Samani, Aqil Tariq, Shahrbanoo Abbasi Jondani, Nazih Y. Rebouh
• DOI: 10.1016/j.ijsrc.2025.11.005

Research Groups

• Reclamation of Arid and Mountainous Regions Department, Faculty of Natural Resources, University of Tehran, Iran
• Department of Wildlife, Fisheries and Aquaculture, Mississippi State University, Mississippi State, MS, USA
• Institute of Environmental Engineering, RUDN University, Moscow, Russia

Short Summary

This study evaluated and calibrated the GeoWEPP model to predict runoff and sediment yield in the mountainous Amameh watershed, Iran, incorporating snowmelt dynamics and high-resolution spatial data. It assessed eight biological conservation scenarios, demonstrating that enhanced canopy cover can reduce runoff by up to 44% and sediment yield by up to 47%.

Objective

• Evaluate and validate the GeoWEPP model for predicting runoff and sediment yield in the mountainous Amameh watershed, Iran, under complex conditions, with a specific focus on snowmelt dynamics and the application of high-resolution spatial data.
• Assess the impact of eight biological conservation scenarios, including incremental increases in canopy cover and expanded channel cover, on watershed behavior (runoff and sediment yield).

Study Configuration

• Spatial Scale: Amameh watershed, Latyan Basin, Iran, covering an area of 37.95 km². Elevation ranges from 1790 m to 3896 m. Utilized a high-resolution Digital Elevation Model (DEM) with a 10 m x 10 m spatial resolution.
• Temporal Scale: Climate data from 2000 to 2017 (17 years). NDVI maps represent a 17-year average (2001-2017). Simulations were conducted over a 17-year period. Daily streamflow data from 2001 to 2017 were used for calibration and validation.

Methodology and Data

• Models used: GeoWEPP (Geospatial interface for the Water Erosion Prediction Project), WEPP (Water Erosion Prediction Project), CLIGEN (weather generator), TOPAZ (topographic parameterization software).
• Data sources:
  • Climate: Daily meteorological data (precipitation, maximum/minimum temperatures, solar radiation, dew point temperature, wind magnitude and azimuth) from Tehran synoptic meteorological station (2000-2017). Snowfall coefficient (0.69) derived from hydrological research.
  • Topography: Digital Elevation Model (DEM) with 10 m spatial resolution, prepared from 1:25,000 topographic maps.
  • Soil: Regional soil survey report, field observations, and laboratory analyses for initial soil characteristics (sand, silt, albedo, organic matter, texture). Erodibility parameters (saturated hydraulic conductivity, interrill erodibility, rill erodibility, critical shear stress) were estimated via GeoWEPP internal equations and calibrated.
  • Land Use/Land Cover (LULC) / Plant/Management: Base land use map from the General Department of Natural Resources and Watershed Management of Tehran Province (2012a), modified for spatial resolution. Field monitoring, regional data, and remote sensing (17-year average NDVI 2001-2017). Rangeland classification reports (Tehran Province Natural Resources Office, 2012).
  • Observed Data: Yearly soil loss measured in the field, and daily streamflow data from Kamarkhani hydrometry station (2001-2017).

Main Results

• The calibrated GeoWEPP model showed good performance in predicting runoff (Nash-Sutcliffe Efficiency (NSE) = 0.74, R² = 0.84) and sediment yield (NSE = 0.64, R² = 0.51).
• The average annual rainfall was 25,193,216 m³/yr, resulting in an average annual flow of 957,013 m³/yr (equivalent to 0.65 m³/s). The total simulated sediment yield was 219,390.8 tonnes/yr.
• The average specific sediment yield estimated by the calibrated model (18.7 tonnes per hectare per year) was very close to the observed average (18.59 tonnes per hectare per year).
• Calibration revealed that rill erodibility (Kᵣ) and critical shear stress (τc) were the most sensitive parameters for sediment yield, while saturated hydraulic conductivity (Kₑ) had a greater influence on runoff.
• Eight biological conservation scenarios, primarily involving increased canopy cover, demonstrated significant reductions in runoff and sediment yield:
  • Enhancing canopy cover could lower runoff by up to 44.58% and 47.01% in two combined scenarios.
  • Enhancing canopy cover could lower sediment yield by up to 54.36% and 56.76% in two combined scenarios.
  • A specific channel-cover scenario (Modified-1) resulted in reductions of up to 51.37% in runoff and 67.03% in sediment yield.
• The river experiences peak discharge and highest sediment yield in the spring and summer months, largely attributed to snowmelt dynamics.

Contributions

• First application and validation of the GeoWEPP model in the Amameh watershed, Latyan Basin, Iran, specifically addressing complex mountainous conditions, snowmelt dynamics, and utilizing high-resolution spatial data.
• Successful integration of additional modeling for meltwater runoff to overcome GeoWEPP's initial limitations in accurately estimating summer runoff in snowmelt-dominated regions.
• Development and utilization of a fully localized CLIGEN dataset from site-specific observations for Iran, thereby reducing uncertainties associated with non-representative weather statistics.
• Quantitative assessment of the impact of eight biological conservation scenarios (increased canopy cover and expanded channel cover) on watershed runoff and sediment yield, providing empirical insights for sustainable land management.
• Identification of key sensitive soil parameters (rill erodibility, critical shear stress, and saturated hydraulic conductivity) crucial for accurate erosion predictions in the study area.

Funding

The authors acknowledge Professor Assefa M. Melesse for language editing and review. No specific funding projects, programs, or reference codes were explicitly listed in the paper.

Citation

@article{Lari2025Quantifying,
  author = {Lari, Masoumeh and Samani, Aliakbar Nazari and Tariq, Aqil and Jondani, Shahrbanoo Abbasi and Rebouh, Nazih Y.},
  title = {Quantifying sediment yield and discharge fluctuations using the GeoWEPP in response to soil and water conservation practices},
  journal = {International Journal of Sediment Research},
  year = {2025},
  doi = {10.1016/j.ijsrc.2025.11.005},
  url = {https://doi.org/10.1016/j.ijsrc.2025.11.005}
}