The Chui Valley is located on the northern edge of the Kyrgyz Republic. The Kyrgyz part of the valley covers the relatively extensive left bank of the Chu River from the meridian of the Boom Gorge in the east to the upper and middle reaches of the river (Aspara) Ashmara, a right tributary of the Kuragaty River in the west. The valley stretches in a latitudinal direction from west to east over a distance of 200 km, and 100 km from north to south at its widest point. To the west and northwest, the valley is open and gradually transitions into the vast sandy desert of Moyun-Kum. The lowest elevations (570-590 m) are observed in the north and northwest near the Tashatkyl Reservoir. To the south and southeast, the elevation increases near the village of Dzhiel-Aryk and reaches 1250 m. Thus, there is a general slope of the plain from east to west, which, along with the slope to the north and northwest flow of the Chu River, has determined its shape.
The Chu River divides the valley into two unequal parts, causing the asymmetry of its cross-section, with a wide left bank (up to 100 km) and a narrow right bank (up to 10 km).
The bottom of the Chui Valley is composed of loose sedimentary deposits, predominantly represented by gravel, sometimes with layers of sand and gravel. Closer to the mountains of the Kyrgyz Ridge, in the foothill zone, the surface formations are represented by powerful coarse-grained debris flows from mountain rivers and temporary watercourses.
Orography
To the south, the Chui Valley is framed by the Kyrgyz Ridge (Fig. 1). In the extreme east, its spurs, known as the Kyzyl-Ompol Mountain, reach a height of 3180 m and do not reach the shores of Lake Issyk-Kul. From this spur, the Kyrgyz Ala-Too extends westward to the Kara-Balta Pass in a latitudinal direction. Then, the axial ridge of the ridge in the western part of the Chu River basin sharply changes its direction from latitudinal to meridional and forms an oval-shaped protrusion directed northward. West of the basin of the Zharly-Kaindy River, the axial ridge aligns again, but acquires a sublatitudinal direction and ends near the city of Taraz (Jambyl region).
In a straight line, the total length of the Kyrgyz Ridge within the specified limits is 360 km, and taking into account the main bends, it is 410 km. Rising near the city of Taraz only 50 m above the river Talas and 640 m above sea level at the Tekturmasa Mountains, the Kyrgyz Ridge gradually increases in height to the east. Between the sources of the Chonor and Makmal-Chal rivers, it rises above the snow line, reaching heights of 3750-3850 m. Further, the ridge again decreases to 2700-2800 m. South of the village of Merke, starting from the basin of the river of the same name in the area of the Kok-Kiya Pass, the heights again increase to 4100-4200 m at the junction of the basins of the Zharly-Kaindy, Chon-Kaindy, and Karakol rivers of the Talas region. Further, the ridge again decreases in the middle part of the Kara-Balta River basin to elevations of 3500-3600 m. But at the sources of the Kara-Balta River (from the Tyo-Ashuu Pass), the heights immediately increase, and the ridge again rises above the snow line. At the meridian of Bishkek, the heights reach 4500-4800 m. A similarly high part of the ridge, but slightly lower at 4200-4400 m, extends eastward to the Shamsy Pass. East of this pass, the axial ridge of the ridge reaches 4000-3800 m, steeply descending to the east towards the Kerke Pass and further to the basin of the Tunduk River.
An important feature of the orography of the Kyrgyz Ridge is that its axial ridge is somewhat shifted to the south of the highest peaks, which are located on the lateral spurs that extend northward.
On the northern slope of the Kyrgyz Ridge, numerous lateral spurs of meridional and closely related orientations extend from the axial ridge. These include the Ala-Archinsky, Alamudunsky, Sokuluksky, Issyk-Ata, and other spurs. The highest elevations of the Kyrgyz Ala-Too are associated with the first of these - the western Alamudun Peak (4895 m). At least 10 peaks of this massif have heights of 4700-4800 m. In the Alamudun spur, the Kyrgyzstan massif rises (4840 m). The continuation of the Alamudun spur is the Ken-Tor spur (4200 m), while the Issyk-Ata spur has a height of 4550 m, and others. On the watershed ridge between the basins of the Noryuz and Issyk-Ata rivers is the peak of the Communist Party of Kyrgyzstan (4483 m).
To the west of the axial ridge of the ridge, several fan-shaped diverging mountain spurs extend, forming private watersheds between river basins. The largest of these are the Ak-Suisky with heights of 4454 m, the Kara-Baltinsky, which rises in the middle part to elevations of 4100-4200 m, the hard-to-reach Chon-Kaindy (4410 m), the Zharly-Kaindy (4260 m), the Ashmirinsky with a height of 4243 m, and the Merken (4150 m).
