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# Scale issues in hydrological modelling: A review

## Details

**Authors** Blöschl, G. and Sivapalan, M.

**Year** 1995

**Publisher** Hydrological Processes

**Kind of work** article

**Discipline** Hydrology

**Secondary disciplines** Geography, Environment & Sustainability

**Applied** false

[Read it at the publisher](https://doi.org/10.1002/hyp.3360090305) 
10.1002/hyp.3360090305

## In authors' words

### What they set out to do (purpose)

To review how scale is defined and handled in hydrological modelling, and to identify the key issues and research directions for scaling.

### What they found (results)

The review separates process scale, observation scale and modelling scale, and notes that these terms are often used inconsistently. It describes upscaling as two steps, distributing and aggregating, and downscaling as disaggregation and singling out. It treats heterogeneity and variability in catchments as bearing on how randomness and organization affect scaling. It contrasts modelling-based approaches with a holistic approach based on dimensional analysis and similarity concepts.

## Commentary

### In short

The review shows hydrologists separating the scale at which a process operates from the scale at which it is observed and the scale at which it is modelled. This amounts to the recognition that what is seen of a catchment depends on the vantage point of measurement. Its treatment of upscaling as aggregation of parts into a whole, and of downscaling as disaggregation, describes a part-whole structure across levels.

**Patterns it shows** S, P

Shows the structure is there

**Added** 2026-10-09

**How to cite this** Blöschl, G. and Sivapalan, M. (1995). Scale issues in hydrological modelling: A review. Hydrological Processes.