Chapter 33 Chapter Seven Ningxia Ancient Irrigation District
Ningxia Plain is located in the northern part of Ningxia Hui Autonomous Region, with east longitude 105°-107° and north latitude 37°30′-39°30′.It is a long and narrow plain, running from southwest to northeast, 320 kilometers long, 10-40 kilometers wide, with an area of 17,000 square kilometers, accounting for about 1/4 of the entire autonomous region.It can be divided into two small plains with Qingtong Gorge as the boundary, the Yinchuan Plain in the northeast, which is slightly larger; the Weining Plain in the southwest, which is slightly smaller.The whole plain is formed by the alluvial deposits of the Yellow River and the flood deposits of the Helan Mountains, with an altitude of 1100-1200 meters, with deep, fertile and heavy soil.
Because it belongs to the middle latitude and the altitude is not too high, it is relatively warm. Taking Yinchuan in the center of the plain as an example, the average monthly temperature is relatively cold in January, which can drop to minus 10°C.But by March, it rose above zero.By July, the monthly average is as high as 24°C.After November, it dropped below zero again.From the perspective of temperature, this area is suitable for the growth of crops.
However, it is far away from the sea, surrounded by highlands and deserts, with the Mu Us Sandy Land in the east, the Helan Mountain and Tengger Desert in the west, the Loess Plateau in the south, and the Ulan Buh Desert in the north, so the air is dry. , with very little rainfall.In Yinchuan, the rainfall in six months is below 10 millimeters, and in the other six months it is above 10 millimeters, but the increase is not much. Even in the highest month of July, the annual average is only 31 millimeters.The average annual rainfall for many years is less than 200 milliliters.This amount of rainfall is far from the needs of crop growth.
Although the Ningxia Plain has little rainfall, which is not conducive to the development of agriculture, this unfavorable factor is compensated by another favorable factor, that is, the Yellow River, which is rich in water, just flows through the whole area of the plain. It flows from the southwest end of the plain to the plain. outflow from the northeast end.According to contemporary measurements, the section of the Yellow River above Gansu has a large flow due to its many tributaries and low evaporation. When it enters Ningxia, the annual runoff is 35 billion cubic meters.Therefore, as long as measures are taken according to local conditions, water conservancy projects are built on the plains to irrigate with water from the Yellow River, and most of the land in the Ningxia Plain can be reclaimed as farmland.
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