Improving water quality in China: Environmental investment pays dividends
Graphical abstract
Introduction
Inland waters such as lakes, reservoirs, streams, rivers, etc, provide a wide variety of ecosystem services ranging from potable water, to sources of food, through to transportation and sites for recreation (Downing et al., 2006). However, these inland water ecosystems are threatened across the planet by the dual pressure of anthropogenic activities and climate change (Bragazza et al., 2012, Feng et al., 2008, Williamson et al., 2014). Land use intensification and urbanization have resulted in increased discharge of wastewater from households, agriculture, and industry, resulting in an elevated risk of point and non-point source pollution (Foley et al., 2005, Zhou et al., 2016). Eutrophication is a common consequence of deteriorating water quality and is a state characterized by high nutrient levels, low water transparency, and excessive growth of algal cells (Paerl et al., 2011a, Paerl et al., 2011b, Qin et al., 2015). Blooms of toxic and hypoxia-generating cyanobacteria are an indicator of advanced eutrophication and represent a serious threat to potable water supplies and the ecological sustainability of inland water ecosystems (Paerl and Huisman, 2008, Paerl and Otten, 2013). Therefore, protection of inland waters is required to safeguard the quality and safety of the myriad of ecosystem services that these waters provided to consumers (Guo, 2007, Paerl and Huisman, 2008). Furthermore, primary production and land use practices within a watershed impact greenhouse gas emissions from inland waters, as for example organic carbon is metabolized to carbon dioxide (CO2) and/or methane (CH4) and nitrogenous compounds are transformed to nitrous oxides (N2O) (Butman and Raymond, 2011, Davidson et al., 2015, Maberly et al., 2012, Weyhenmeyer et al., 2015). Knowledge of impacts on water quality in inland waters, and the associated drivers, are therefore of great importance to obtain a better understanding of their role in the global carbon cycle (Bianchi, 2011, Li et al., 2016, Maberly et al., 2012, Piao et al., 2009) and to allow for implementation of measures to protect inland freshwater resources (Williamson et al., 2008, Williamson et al., 2009).
The water quality of inland waters is determined by numerous factors such as land use, hydrologic conditions, and anthropogenic activities (Kellerman et al., 2014, Kothawala et al., 2014). The effects of the morphological features of a lake, including depth, surface area, and water retention time, on trophic levels have been widely investigated (Nõges et al., 2003, Nõges, 2009), and many studies have been undertaken to elucidate the relationships between water quality and watershed land use (Carney, 2009, Kothawala et al., 2014, Liu et al., 2011, Müller et al., 1998, Maberly et al., 2003, Stedmon and Markager, 2005, Taranu and Gregory-Eaves, 2008). However, most studies to date have been conducted in lakes with similar land use in their watersheds and with comparable lake morphometric characteristics, and typically have limited spatial and temporal resolution. Furthermore, the majority of the studies have focused on direct relationships between water quality and the corresponding flow rate at different time scales (i.e. daily/weekly/monthly) (Chen et al., 2015, Goldman et al., 2014, Guo et al., 2014, Koch et al., 2013, Stedmon and Markager, 2005, Striegl et al., 2005). Generally, population density and industrial development have been considered important driving factors of declining water quality in inland waters (Duan et al., 2009). The gross domestic product (GDP) offers one measure of development that can be analyzed. However, the population density and economic statistical data presented in the limited number of studies linking these metrics to water quality are frequently estimated from information derived from statistical yearbooks published by various administrative units (Duan et al., 2009, Huang et al., 2014). In most cases, though, administrative units do not encompass the whole watershed. Further investigation into the direct relationships between water quality, human population density and GDP of individual watersheds is therefore required to assess the role these metrics may play in determining the health of inland waters.
In China, eutrophication coupled with environmental degradation has been considered as one of the prices paid for the rapid economic development occurring since the “reform and opening up-policy” was introduced in the late 1970s (Liu and Diamond, 2005, Liu et al., 2013). Importantly, in recent years, measures to remedy eutrophication have been introduced such as the Natural Forest Conservation Program (NFCP) and the Grain to Green Program (GTGP, also known as the Sloping Land Conversion Program and the Farm to Forest Program), the world's largest government-financed conservation action programs whose implementation was prompted by severe droughts in 1997 and unprecedented floods in 1998 (Liu et al., 2008, Ouyang et al., 2016). Furthermore, today, billions of RMB Chinese Yuan are dedicated to ecosystem restoration via environmental protection actions (e.g. the establishment of wastewater treatment plants). It is yet to be determined how these actions affect water quality and whether they have effectively reversed anthropogenically induced water quality degradation to any extent.
The objective of this study was to investigate the long-term variations of water quality in Chinese inland waters and to access the factors contributing to changes in water quality. An additional aim was to elucidate how conservation actions introduced by the Chinese government in the past two decades have impacted water quality. To elucidate the dynamics of water quality in Chinese inland waters, weekly data on water quality for the period January 2006 to December 2015 (n = 499) were examined for a total of 145 sites spanning the entire country (Fig. 1). These water quality measurements included dissolved oxygen (DO), chemical oxygen demand (COD), and ammonium (NH4+-N) at all 145 sites. Data on land use and land cover (LULC), population density, and GDP with 1-km spatial resolution and 5-year intervals during the past two decades were analyzed to assess relationships between water quality and the hypothesized driving factors. Government led investments in areas such as environmental restoration and reforestation were further investigated to determine how these actions have impacted the water quality in Chinese inland waters during the past two decades.
Section snippets
Gauged datasets
Water quality, including DO, COD, and NH4+-N, was determined on a weekly basis for a total of 145 monitoring sites in major rivers and lakes in China from January 2006 to December 2015 (Fig. 1). The data were collected by the China National Environmental Monitoring Center (data available at http://www.cnemc.cn/publish/107/0594/350/newList_1.html). The main indices for chemical indicators of different water quality levels were categorized according to the water quality standards for surface
General results on water quality
Water quality for the 145 nation-wide sites was divided into five categories: I to V, ranging from good to poor (Fig. 1) as described in section 2.1. Spatially, water quality levels were notably poorer (dominated by conditions poorer than the characteristics stipulated for level III) in eastern China than in the other regions. This was particularly pronounced for the sites in the North China Plain and the Northeast China Plain (Fig. 1). Accordingly, markedly higher COD and NH4+-N and low DO
Discussion
Our results demonstrate markedly higher COD and NH4+-N levels, lower DO concentrations, and a correspondingly more degraded water quality index in the North China Plain and the Northeast China Plain than in the remaining areas of China. This can primarily be explained by an elevated proportion of developed land use (cities + cropland), higher GDP, and greater population density (Fig. 4; Fig. S1), as highlighted by the relationships between COD, NH4+-N, and the percentage of cities of LULC,
Conclusions
- (1)
Our results demonstrate that the increasing GDP in China over the past decade did not occur at the further expense of its inland water ecosystems. This is particularly evident from the significant and exponentially decreasing GDP-normalized COD and ammonium (NH4+-N) concentrations throughout the country, coinciding with increasing government-financed environmental investments during the past two decades.
- (2)
This offers hope for the future, also for other industrializing countries, that with
Acknowledgments
This work was supported by the National Natural Science Foundation of China (grants 41621002, 41601537, 41325001, and 41230744) and International Scientific Cooperation Project (2014DFG91780). Erik Jeppesen was supported by the MARS project (Managing Aquatic ecosystems and water Resources under multiple Stress) funded under the 7th EU Framework Programme, Theme 6 (Environment including Climate Change), Contract No.: 603378 (http://www.mars-project.eu), ‘CLEAR’ (a Villum Kann Center of
References (61)
- et al.
Understanding the influence of suspended solids on water quality and aquatic biota
Water Res.
(2008) - et al.
Investigating organic matter in Fanno Creek, Oregon, Part 3 of 3: identifying and quantifying sources of organic matter to an urban stream
J. Hydrology
(2014) - et al.
Satellite data regarding the eutrophication response to human activities in the plateau lake Dianchi in China from 1974 to 2009
Sci. Total Environ.
(2014) - et al.
Spatial and temporal patterns of China's cropland during 1990–2000: an analysis based on Landsat TM data
Remote Sens. Environ.
(2005) - et al.
Controlling harmful cyanobacterial blooms in a world experiencing anthropogenic and climatic-induced change
Sci. Total Environ.
(2011) - et al.
Controlling harmful cyanobacterial blooms in a hyper-eutrophic lake (Lake Taihu, China): the need for a dual nutrient (N & P) management strategy
Water Res.
(2011) - et al.
Cyanobacterial bloom management through integrated monitoring and forecasting in large shallow eutrophic Lake Taihu (China)
J. Hazard. Mater.
(2015) - et al.
Recent changes of sediment flux to the western Pacific Ocean from major rivers in East and Southeast Asia
Earth-Science Rev.
(2011) - et al.
Downstream sedimentary and geomorphic impacts of the three Gorges dam on the Yangtze river
Earth-Science Rev.
(2014) - et al.
Dissolved organic matter fluorescence at wavelength 275/342 nm as a key indicator for detection of point-source contamination in a large Chinese drinking water lake
Chemosphere
(2016)
The role of terrestrially derived organic carbon in the coastal ocean: a changing paradigm and the priming effect
Proc. Natl. Acad. Sci.
Biogeochemical plant–soil microbe feedback in response to climate warming in peatlands
Nat. Clim. Change
Significant efflux of carbon dioxide from streams and rivers in the United States
Nat. Geosci.
Relative influence of lake age and watershed land use on trophic state and water quality of artificial lakes in Kansas
Lake Reserv. Manag.
FTIR and synchronous fluorescence heterospectral two-dimensional correlation analyses on the binding characteristics of copper onto dissolved organic matter
Environ. Sci. Technol.
Eutrophication effects on greenhouse gas fluxes from shallow-lake mesocosms override those of climate warming
Glob. Change Biol.
The global abundance and size distribution of lakes, ponds, and impoundments
Limnol. Oceanogr.
Two-Decade reconstruction of algal blooms in China's Lake Taihu
Environ. Sci. Technol.
Increased cuticular carbon sequestration and lignin oxidation in response to soil warming
Nat. Geosci.
Global consequences of land use
Science
Global carbon export from the terrestrial biosphere controlled by erosion
Nature
Doing battle with the green monster of Taihu Lake
Science
Runoff-mediated seasonal oscillation in the dynamics of dissolved organic matter in different branches of a large bifurcated estuary-The Changjiang Estuary
J. Geophys. Res. Biogeosciences
Modeled responses of summer climate to realistic land use/cover changes from the 1980s to the 2000s over eastern China
J. Geophys. Res. Atmos.
Response of fish and plankton to nutrient loading reduction in eight shallow Danish lakes with special emphasis on seasonal dynamics
Freshw. Biol.
Shallow lake restoration by nutrient loading reduction—some recent findings and challenges ahead
Hydrobiologia
Lake responses to reduced nutrient loading - an analysis of contemporary long-term data from 35 case studies
Freshw. Biol.
Chemodiversity of dissolved organic matter in lakes driven by climate and hydrology
Nat. Commun.
Hydrologic controls on the transport and cycling of carbon and nitrogen in a boreal catchment underlain by continuous permafrost
J. Geophys. Research-Biogeosciences
Controls of dissolved organic matter quality: evidence from a large-scale boreal lake survey
Glob. Change Biol.
Cited by (147)
Trajectory in water scarcity and potential water savings benefits in the Yellow River basin
2024, Journal of HydrologyExploring China's water scarcity incorporating surface water quality and multiple existing solutions
2024, Environmental ResearchA novel framework for integrative assessment of water balance health in China
2024, Journal of Cleaner ProductionThirty years of experience in water pollution control in Taihu Lake: A review
2024, Science of the Total EnvironmentDomestic environmental impacts of OFDI: City-level evidence from China
2024, International Review of Economics and FinanceWidespread decrease in chromophoric dissolved organic matter in Chinese lakes derived from satellite observations
2023, Remote Sensing of Environment
- 1
These authors contributed equally to this study.