Intermontane Basin Subregion (SWIR)
Overview
The SWIR Intermontane Basin is a subregion defined by its large plateau area with a steady elevation range of 1,000m-1,200m. The basin is flanked by the West Coast Ranges to the west, and the ABC Ranges to the south-east. These ranged themselves rise to heights exceeding 4,000m in parts, however the definition of the SWIR cuts the elevation of these ranges at 2,300m - roughly at the treeline. This intermontane subregion is the largest portion of the SWIR, making up about 88% of the region with an area approximately 1,712,480 km².
The soils of the basin area are mostly basaltic. The Western Ranges have an active orogeny, being formed as the oceanic plate to the west is subducted under the Western Kuha plate. The Western Ranges include volcanic mountains and hydrothermal activity in the range foothills, providing the basaltic base of the NIB. The plateau itself was formed by repeated historic volcanic outpourings. Andosol soils can also be found around valley floors and flood plains of the Dau River, as well as pockets of loess soils across the grasslands areas.
The Intermontane Basin has two areas: the cold semi-arid steppe land in the north (~36°–40°N) and cool to warm mediterranean climate in the south (~33°-36°N) with dry summers and wet winters. Each will be discussed in their own subsections below. Summary tables are at the end of each subsection.
Northern Intermontane Basin
The Northern Intermontane Basin (NIB) is a transition zone between semi-/arid regions to its north and the more humid mediterranean subregion of SWIR to its immediate south. The northern extreme of the intermontane basin transitions into steppe woodland and grassland, and sees snowfall at the coldest times of the year. Immediately north of this steppe lies the [[North Western Tundra Belt (NWTB)]]; to the north east, the [[Western Kuha Steppe]]; to the east, the [[Notes/South Western Cool Desert Region]].
Unlike the [[SWIR Escarpment (Astro)]], precipitation in the NIB is year-round, with an annual amount of 500mm - 650mm. Due to the regular precipitation, the basin area has many minor water run offs that feed into the Dau River.
The average annual temperature is roughly 3 to 6°C; a figure that masks the range of temperatures felt across the seasons. Winter mean temperatures can range between -5 to -10°C, with the absolute minimum ranging between -18 to 22°C. This results in snowpack during most of the winter, and the freezing of the braided channels of the Dau River. Summer means stay roughly between 15 to 19°C, but peaks can reach between 26 to 30°C.
| Attribute | Value |
|---|---|
| Latitude | 36° - 41°N |
| Köppen Climate Classification | Cold semi-arid steppe (Bsk), |
| Ecoregion | Cold steppe and temperate grassland, riparian zone along the Dau River |
| Precipitation | Even annual distribution of 500mm – 650mm |
| Annual mean temperature range | 3°C -6°C |
| Winter mean range | −5 to −10°C |
| Summer mean range | 15–19°C |
| Elevation range | 1,000m – 2,300m (mountain range inclusive) |
| Tree line | 2,300m |
| Area | ~1,946,000 km² |
The landscape of the NIB is relatively homogenous with it’s flat plateau. Dominated by grasslands, the NIB has near non-existant tree coverage, though the riparian zone along the Dau River sees some trees. The Dau River shows multiple channels, with meandering braids across the terrain. At peak flows in spring, the channels may widen up to 20km, making travel hazardous and challenging. This dynamism of the Dau results in channels gradually migrating every few years.
NIB Mountain Range Foothills
Closer to the foothill of the Western Ranges sees a micro-climate area distinct from the open pleataeu. This area has denser scrubs and woodlands of sturdy varieties that withstand the dryness and warmth of Föhn winds. The Föhn winds results in a modestly higher annual mean temperature (+1 to 2°C), with weaker snow pack and a longer growing season. Consequently, the foothills of the Western Ranges has historically been occupied by various peoples who take advantage of the particularities of this area.
Seasonal Experience
While the seasons of Kuha are astronomically equal in length (each season ~102-103 days), the seasonal experience in NIB is of long winters and summers. Experiential Winter and Summer, defined by temperatures, lasts between 120-130 days while Experiential Spring and Autumn are much shorter (60-70 days). Winter is experienced as longer due to the snow pack lasting well beyond the spring equinox, and the arrival of subzero temperatures only shortly after the autumnal equinox (around Month 11). Summer is defined by its dryness and warmth, and fades gradually into a short autumn where mean temperatures are below 10°C but above 0°. Spring is the most dramatic season with a rapid temperature increase and accompanying snow melt.