Spatial and temporal analysis of water chemistry records (1958–2000) in the Huanghe (Yellow River) basin

Abstract

The chemistry of major dissolved ions (Ca2+, Mg2+, Na+ + K+, HCO3−, SO42−, Cl−) and dissolved silica (SiO2) in the river water of the Huanghe (Yellow River), China, was studied from historical records at 100 stations in the drainage basin for the period 1958–2000 (not all the parameters were continuously monitored during the entire period). This river system (750,000 km2) presents an exceptional temporal and spatial water chemistry variability compared to other major rivers. The total dissolved solid (TDS) concentration of the Huanghe varied over 2 to 3 orders of magnitude throughout the basin, with a median TDS concentration of 452 mg/L, which is about 4 times the world spatial median value (WSM). In particular, the concentrations of Na+ + K+, SO42−, and Cl− were 10–20 times higher than in other major world rivers. Similar to the Changjiang (Yangtze River) and many other Himalayan rivers, the TDS at a given station is seasonally variable and inversely related to river runoff with a variation factor less than 2.0, despite a water dilution of fourfold to fivefold in the summer flood season. In addition to chemical weathering of sedimentary rocks, evaporation and fractional crystallization were found to be the major natural process controlling the major element chemistry of the Huanghe, owing to the abundance of loess and clastic rocks under arid and semiarid climates. A persistent increasing trend from year to year has been observed in the concentrations of TDS and all the salts except for HCO3− at all main‐channel stations except for the uppermost Lanzhou. The rate of increase in the TDS concentration was the highest in the middle reaches (10.52 mg/L yr−1 at Toudaoguai) and remained to be unusually high in the lower reaches (5.5 mg/L yr−1 at Stations Luokou and Lijin). The increasing trend coincided with a significant decrease in water discharge at most of the main‐channel stations in the past 40 years, and is attributed to increasing regulations of reservoirs and intensive water withdrawal for irrigation and diversions, as well as many other anthropogenic processes. Despite the increasing trend in TDS concentrations, the seaward TDS flux to the sea by the Huanghe has decreased dramatically from more than 20 × 109 kg/yr in the 1960s to less than 10 × 109 kg/yr at present, due to the sharp decrease in water discharge (sometimes completely dried up) in the lower reaches of the river. The significant decreases in sea‐ward fluxes of water and dissolved salts are expected to have profound physical, ecological, and socio‐economic impacts on the lower reaches of the river, the coastal areas and the Bohai Sea.

Concentration–discharge relationships reflect chemostatic characteristics of US catchments

“…As an example, the seaward total dissolved solids flux from the Huanghe (Yellow) River, China has decreased by more than half over the last approximately 40 years because of a sharp decrease in water discharge in the lower reaches of the river (Chen et al, 2005). Diversions, irrigation and reservoir use are primarily responsible for the decrease in water discharge, and despite an increase of ¾5 to 10 mg/l/year in total dissolved solids in the middle and lower reaches of the river, there has been an overall decrease in solute flux (Chen et al, 2005). Climate change models predict that flows in the southwestern United States and other dry areas are likely to decrease by 10 to 40% by 2090-2099 relative to 1980-1999 scenario in which global average temperatures increase by 2Ð8°C over the same period (IPCC, Core Writing Team, 2007).…”

A comparative overview of weathering intensity and HCO3− flux in the world's major rivers with emphasis on the Changjiang, Huanghe, Zhujiang (Pearl) and Mississippi Rivers

“…These three values were 1.95, 3.53 and 3.58 mM in Aug, Feb, and Mar, 2001, respectively. Based on the knowledge that discharge in the wet season (August) is about 3 times of that of the dry season (Feb) and that the duration of the wet season is about 4 months compared to about 8 months for the dry season (Chen et al, 2005), we calculated that the discharge-weighted [HCO 3 À ] is 2.59 mM and its flux is 122 Â 10 9 mol yr…”

“…The Huanghe (Yellow River) ranks low in the world's large rivers in terms of its water discharge (average in 1919-1995 is 58 Â 10 9 m 3 yr À1 ; Chen et al, 2005Chen et al, , 2006, but it ranks among the top one or two world rivers in terms of suspended sediment load (average in 1950s-1970s is 1.6 Â 10 15 g yr À1 ) with only a medium sized drainage basin area (0.75 Â 10 6 km 2 , Chen et al, 2005Chen et al, , 2006. The upper watershed, also from the Qinghai-Tibet Plateau, supplied 60% of the source water, but only 10% of the sediment (Zhang et al, 1995).…”

“…Most of the voluminous suspended sediments come from the Loess Plateau (average thickness is 130-180 m) located in the mid reach of the river (which covers 40% of the entire drainage basin) (Zhang et al, 1995). The glacial loess deposits in northern China are some of the largest and thickest in the world and were formed by dust fall, following a major climate shift in the Early Pleistocene about 2.5 Ma ago and throughout the entire Quaternary (Chen et al, 2005). In addition to loess, outcrops of Archean to Tertiary granites and metamorphic rocks can be found in the Huanghe drainage basin (Zhang et al, 1995).…”

Hydrochemistry and its controlling factors of rivers in the source region of the Yangtze River on the Tibetan Plateau

“…In China, most studies have focused on the Yangtze River (Chen et al, 2002;Li and Zhang, 2005), the Yellow River (Chen et al, 2005), the Han River (Li et al, , 2009, and the Huai River (Zhang et al, 2011). However, there have been only a few studies on the hydrochemistry of the river water in SRYR.…”