HBV-Lab 1.1.1

An intuitive, object-oriented and user-friendly Python implementation of a lumped conceptual HBV hydrological model for educational and research purposes.

HBV_Lab

An intuitive, object-oriented Python implementation of a lumped conceptual HBV rainfall–runoff model, with built-in calibration and uncertainty analysis.

HBV is a widely used conceptual hydrological model that simulates the main processes governing the transformation of precipitation into streamflow — snow accumulation and melt, soil moisture accounting, groundwater storage, and channel routing [1]. It has been implemented in many software packages and operational products [2] [3].

HBV_Lab is a clean, transparent reimplementation in Python designed to be easy to read, easy to use, and easy to teach with. Every routine is exposed as a small, well-documented function, and the full model is wrapped in a single HBVModel object that handles data loading, simulation, calibration, uncertainty analysis, plotting, and persistence. It is well suited to research prototyping, method development, and hydrology education.

Scope at a glance: lumped (single-cell, spatially averaged) · conceptual · daily time step · requires precipitation, temperature and potential evapotranspiration as input · 14 calibratable parameters. Please read Scope, Assumptions & Limitations before using results in any decision-making context.

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Features

• Complete HBV structure — snow, soil, groundwater response (two reservoirs, three runoff components) and MAXBAS triangular routing.
• Object-oriented API — one HBVModel object holds data, parameters, states and results.
• Automatic calibration — single-objective optimisation (NSE, KGE, RMSE or MAE) via SciPy, using a gradient-free optimiser by default (see note on calibration).
• Uncertainty analysis — Monte-Carlo sampling of the parameter space with prediction-interval estimation (GLUE-style).
• Performance metrics — NSE, KGE′, percent bias (PBIAS), RMSE, MAE and correlation, with a configurable warm-up period excluded from evaluation.
• Flexible data loading — CSV or Excel, flexible date parsing, optional expansion of 12 monthly mean PET values to a daily series.
• Rich plotting and save/load of both results (CSV) and the full model (pickle).
• Interactive playground for exploring how each parameter shapes the hydrograph.

Model structure & parameters

The 14 parameters belong, conceptually, to four routines:

parameters = {
    'snow':     ['TT', 'CFMAX', 'SFCF', 'CFR', 'CWH'],
    'soil':     ['FC', 'LP', 'BETA'],
    'response': ['K0', 'K1', 'K2', 'UZL', 'PERC'],
    'routing':  ['MAXBAS'],
}

In the model object the parameters are stored in three groups — snow, soil and response — with the routing parameter MAXBAS held inside the response group. Each parameter is a dictionary with min / max / default values (the ranges are used by calibration and uncertainty analysis):

model.set_parameters({
    'soil':     {'FC': {'min': 50, 'max': 500, 'default': 250}},
    'response': {'MAXBAS': {'default': 4}},
})

A diagram of a single model time step is available here.

Installation

From PyPI:

pip install HBV_Lab

Inside a notebook:

!pip install HBV_Lab

From source (latest development version):

git clone https://github.com/abdallaox/HBV_python_implementation.git
cd HBV_python_implementation
pip install -e .

Requires Python ≥ 3.7. Core dependencies (numpy, pandas, scipy, matplotlib, tqdm, openpyxl) are installed automatically. The interactive playground additionally needs Bokeh (pip install "HBV_Lab[playground]").

Quick start

import pandas as pd
from HBV_Lab import HBVModel

# 1. Load forcing data: a DataFrame with date, precipitation, temperature,
#    potential ET and — optionally — observed discharge columns.
df = pd.read_excel("data/test_data_2.xlsx")
model = HBVModel()
model.load_data(
    data=df,
    date_column="Date", precip_column="P", temp_column="T",
    pet_column="PET", obs_q_column="Q",
    date_format="%Y%m%d", warmup_end="19811231",
)

# 2. (Optional) override default parameter ranges / values
# model.set_parameters({'soil': {'FC': {'default': 250}}})

# 3. Run, calibrate and analyse
model.run()
model.calibrate()              # gradient-free optimisation by default
model.evaluate_uncertainty()   # Monte-Carlo uncertainty analysis
model.plot_results()

# 4. Persist results and the model itself
model.save_results("results/run.csv")
model.save_model("models/my_model")
model = HBVModel.load_model("models/my_model")

The example dataset (data/test_data_2.xlsx) ships with the source repository, not with the PyPI package. Clone the repo, or point load_data at your own data.

Tutorial

A complete, annotated case study — build a model, calibrate it on one period, validate it on another, and quantify parameter uncertainty — is provided in the notebook quick_start_guide.ipynb.

Play with HBV

Build intuition for how each parameter shapes the hydrograph in the interactive HBVLAB playground, which runs a model built with this library.

Inputs & outputs

Inputs (daily, consistent units): precipitation (mm), air temperature (°C) and potential evapotranspiration (mm). PET may be supplied as a full daily series or as 12 monthly means, which are expanded automatically. Observed discharge (mm) is optional but required for calibration, uncertainty analysis and performance metrics. All water fluxes and storages are expressed in millimetres of water depth over the catchment (mm).

Outputs: simulated discharge and its quick / intermediate / base-flow components, plus the full internal state and flux time series (snow pack, liquid water, soil moisture, recharge, actual ET, upper/lower storage). When observed discharge is available, performance metrics (NSE, KGE′, PBIAS, RMSE, MAE, correlation) are computed over the post-warm-up period.

A note on calibration

Because the model contains many threshold operations, its objective surface is piecewise-constant. Gradient-based optimisers (e.g. SLSQP, L-BFGS-B) see near-zero numerical gradients and tend to stop at the starting point without improving the fit, so calibration uses a gradient-free method (Nelder-Mead) by default. The optimiser performs a single-objective, local search; for a more thorough exploration of the parameter space, run evaluate_uncertainty() (Monte-Carlo) or calibrate from several starting points.

Scope, Assumptions & Limitations

HBV_Lab is intended for education and research. To use it with confidence, please be aware of the following:

• Lumped & conceptual. The catchment is treated as a single spatially averaged unit. There is no elevation banding, sub-basin discretisation, or explicit spatial variability. Parameters are effective, calibrated quantities rather than directly measurable physical properties.
• Daily time step. The model is designed and tested for daily forcing. Other time steps are not validated, and several parameters (e.g. the degree-day factor CFMAX, recession coefficients) are defined per day.
• PET is an input. The model does not compute potential evapotranspiration internally; you must supply it (a daily series or 12 monthly means).
• Implementation variant. This is an independent reimplementation of the HBV concept. Specific choices — the order in which recharge and evapotranspiration are evaluated within the soil routine, the two-reservoir response structure, the use of the modified KGE′ (Kling et al., 2012) variability ratio, and the triangular MAXBAS weights — mean results may differ from other HBV implementations such as HBV-light. It has not been benchmarked against an operational HBV code, and it is not affiliated with any official HBV product.
• Calibration caveats. Calibration optimises a single objective with a local search and can settle in local optima; good performance on a calibration period does not guarantee good performance elsewhere. Always validate on an independent period and inspect the hydrograph, not just the summary metrics.
• Uncertainty analysis uses uniform Monte-Carlo sampling and reports prediction intervals from the best-performing runs (a GLUE-style approach). These are indicative, not formal Bayesian posterior intervals.
• Numerical robustness. Inputs are assumed to be clean and gap-free; missing/NaN values in the forcing data are not imputed. Observed-discharge gaps (NaN) are skipped in metric calculations.
• Not for operational decision-making (e.g. flood forecasting or water-resource operations) without independent, site-specific validation by a qualified hydrologist.

Disclaimer. This software is provided "as is", without warranty of any kind, under the terms of the MIT License. The authors accept no liability for any use of the model or its outputs. Verify results independently before relying on them.

Project status

• Actively maintained; current release: v1.1.0 (changelog via releases).
• Core routines and the HBVModel API are covered by a unit-test suite (pytest) and exercised end-to-end by the case-study notebook.
• The API is considered stable for the documented methods; internal helpers may change.

Contributing & support

Bug reports, questions and contributions are welcome via GitHub issues and pull requests. When reporting a problem, a minimal reproducible example (data snippet + code) is greatly appreciated.

Citation

If you use HBV_Lab in academic work, please cite this repository and the foundational HBV references below. A CITATION entry can be provided on request.

License

Released under the MIT License. © Abdalla Mohammed.

References

[1] Bergström, S., & Forsman, A. (1973). Development of a conceptual deterministic rainfall-runoff model. Hydrology Research, 4, 147-170.

[2] Seibert, J., & Vis, M. J. P. (2012). Teaching hydrological modeling with a user-friendly catchment-runoff-model software package. Hydrology and Earth System Sciences, 16(9), 3315-3325. doi:10.5194/hess-16-3315-2012

[3] AghaKouchak, A., Nakhjiri, N., & Habib, E. (2013). An educational model for ensemble streamflow simulation and uncertainty analysis. Hydrology and Earth System Sciences, 17(2), 445-452. doi:10.5194/hess-17-445-2013

[4] Kling, H., Fuchs, M., & Paulin, M. (2012). Runoff conditions in the upper Danube basin under an ensemble of climate change scenarios. Journal of Hydrology, 424–425, 264–277. doi:10.1016/j.jhydrol.2012.01.011