> For the complete documentation index, see [llms.txt](https://swatplus.gitbook.io/io-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://swatplus.gitbook.io/io-docs/theoretical-documentation/section-2-hydrology/chapter-2-1-surface-runoff/2-1.1-runoff-volume-scs-curve-number-procedure/2-1.1.1-scs-curve-number.md).

# 2:1.1.1 SCS Curve Number

The SCS curve number is a function of the soil’s permeability, land use and antecedent soil water conditions. Typical curve numbers for moisture condition II are listed in tables 2:1-1, 2:1-2 and 2:1-3 for various land covers and soil types (SCS Engineering Division, 1986). These values are appropriate for a 5% slope.

Table 2:1-1: Runoff curve numbers for cultivated agricultural lands (from SCS Engineering Division, 1986)

![\* Crop residue cover applies only if residue is on at least 5% of the surface throughout the year.](/files/XpYAytHN77AckoGRC4gM)

![](/files/jcUovShHN8Ali7jBeuDL)

Table 2:1-2: Runoff curve numbers for other agricultural lands (from SCS Engineering Division, 1986)

![\[2\] Poor: < 50% ground cover or heavily grazed with no mulch;  Fair:  50 to 75% ground cover and not heavily grazed;  Good:  > 75% ground cover and lightly or only occasionally grazed.&#x20;
\[3\] Poor:  < 50% ground cover;  Fair:  50 to 75% ground cover;  Good:  > 75% ground cover. &#x20;
\[4\] Poor: Forest litter, small trees, and brush are destroyed by heavy grazing or regular burning;  Fair:  Woods are grazed but not burned, and some forest litter covers the soil;  Good:  Woods are protected from grazing, and litter and brush adequately cover the soil.](/files/fwRqKjG0kvlL51dcFIzw)

Table 2:1-3: Runoff curve numbers for urban areas (from SCS Engineering Division, 1986)

![\[5\] SWAT will automatically adjust curve numbers for impervious areas when IURBAN and URBLU are defined in the .hru file. Curve numbers from Table 6-3 should not be used in this instance.
\[6\] Poor:  < 50% grass cover;  Fair:  50 to 75% grass cover;  Good:  > 75% grass cover](/files/Cr3zvACuW4aMD9PdfhTw)