Spatio-Temporal Variations in Precipitation Extremes in the Endorheic Hongjian Lake Basin in the Ordos Plateau, China

Abstract

Precipitation extremes have important implications for regional water resources and ecological environment in endorheic (landlocked) basins. The Hongjian Lake Basin (HJLB), as the representative inflow area in the Ordos Plateau in China, is suffering from water scarcity and an ecosystem crisis; however, previous studies have paid little attention to changes in precipitation extremes in the HJLB. In this study, we investigated the spatio-temporal variations of the core extreme precipitation indices (i.e., PRCTOT, R99p, Rx1day, Rx5day, SDII, R1, R10, CWD, and CDD) recommended by the Expert Team on Climate Change Detection and Indices (ETCCDI), and analyzed the climatic dry–wet regime indicated by these extreme indices during 1960–2014 in the HJLB. The results show that the nine extreme indices had large differences in temporal and spatial variation characteristics. All the nine extreme precipitation indices showed a large fluctuation, both in the whole period and in the three detected different sub-periods, with variation magnitudes of 13%–52%. Most extreme indices had non-significant downward trends, while only the consecutive wet days (CWD) had a significant upward trend. The eight extreme wet indices increased from northwest to southeast, while the consecutive dry days (CDD) had the opposite change direction. Each index had a different trend with different spatial distribution locations and areas. The nine extreme indices revealed that the climate in the HJLB has become a drought since the early 1980s. This was specifically indicated by all four extreme precipitation quantity indices (PRCTOT, R99p, Rx1day, Rx5day) and the extreme intensity index (SDII) declining, as well as the number of heavy precipitation days (R10) decreasing. When the dry–wet variations was divided into the different sub-periods, the climatic dry–wet changes of each index demonstrated more inconsistency and complexity, but most indices in the first sub-period from 1960 to the late 1970s could be regarded as a wet high-oscillation phase, the second sub-period after the early 1980s was a relatively dry low-oscillation phase, and the third sub-period after the late 1990s or early 21st century was a dry medium-oscillation phase. It is worth noting that most extreme indices had an obvious positive linear trend in the third sub-period, which means that in the last 20 years, the precipitation extremes showed an increasing trend. This study could provide a certain scientific reference for regional climate change detection, water resources management, and disaster prevention in the HJLB and similar endorheic basins or inland arid regions.

Changes in Lake Area in Response to Climatic Forcing in the Endorheic Hongjian Lake Basin, China

“…The Hongjian Lake Basin (HJLB), with a longitude of 109 • 30 38" E−110 • 5 46" E and latitude of 38 • 51 10" N−39 • 20 20" N, is located in the Ordos endorheic basin in the Yellow River Basin, China [34,42]. The HJLB spans the Inner Mongolia Autonomous Region and Shaanxi Province, with four towns (i.e., Xinjie, Taigesumu, Zhongji, and Erlintu) within the HJLB (Figure 1).…”

“…The Hongjian Lake, shaped like an irregular triangle, is located in the center of the HJLB. Seven seasonal rivers without in situ hydrometric stations flow into the central Hongjian Lake, namely the Maogaitu River, the Zhashake River, the Mudushili River, the Songdao River in the Inner Mongolia Autonomous Region, and the Qibosu River, the Erlintu River, and the Haolai River in Shaanxi Province (Figure 1) [34,39,42]. Based on the hydrological analysis under the projected coordinate system projection of Beijing_1954_GK_Zone_19N, the area of HJLB is approximately 1513.10 km 2 , with an elevation from 1337 m to 1640 m [42].…”

“…Seven seasonal rivers without in situ hydrometric stations flow into the central Hongjian Lake, namely the Maogaitu River, the Zhashake River, the Mudushili River, the Songdao River in the Inner Mongolia Autonomous Region, and the Qibosu River, the Erlintu River, and the Haolai River in Shaanxi Province (Figure 1) [34,39,42]. Based on the hydrological analysis under the projected coordinate system projection of Beijing_1954_GK_Zone_19N, the area of HJLB is approximately 1513.10 km 2 , with an elevation from 1337 m to 1640 m [42]. The HJLB is a typical inland semi-arid and arid region, with an average annual precipitation of 393.0 mm in 1960-2014 and an average annual temperature from −10.0 • C in January to 7.4 • C in July [42].…”

“…Based on the hydrological analysis under the projected coordinate system projection of Beijing_1954_GK_Zone_19N, the area of HJLB is approximately 1513.10 km 2 , with an elevation from 1337 m to 1640 m [42]. The HJLB is a typical inland semi-arid and arid region, with an average annual precipitation of 393.0 mm in 1960-2014 and an average annual temperature from −10.0 • C in January to 7.4 • C in July [42]. The primary vegetation types in the HJLB are grassland, desert, woodland, cropland, and lake water surface [34,42,43].…”

“…The HJLB is a typical inland semi-arid and arid region, with an average annual precipitation of 393.0 mm in 1960-2014 and an average annual temperature from −10.0 • C in January to 7.4 • C in July [42]. The primary vegetation types in the HJLB are grassland, desert, woodland, cropland, and lake water surface [34,42,43].…”