Danjiangkou Reservoir Research Articles

Spatio-temporal distribution of phytoplankton in the Danjiangkou Reservoir, a water source area for the Southto-North Water Diversion Project (Middle Route), China

One of the water source areas of the South-to-North Water Diversion Project is the Danjiangkou Reservoir (DJKR). To understand seasonal variation in phytoplankton composition, abundance and distribution in the DJKR area before water diversion, as well as to estimate potential risks of water quality after water diversion, we conducted an investigation on phytoplankton in the DJKR from August 2008 to May 2009. The investigation included 10 sampling sites, each with four depths of 0.5, 5, 10, and 20 m. In this study, 117 taxa belonging to 76 genera were identified, consisting of diatoms (39 taxa), green algae (47 taxa), blue-green algae (19 taxa), and others (12 taxa). Annual average phytoplankton abundance was 2.01 × 106 ind./L, and the highest value was 14.72 × 106 ind/L (at site 3 in August 2008). Phytoplankton abundance in front of the Danjiangkou Dam (DJKD) was higher than that of the Danjiang Reservoir Basin. Phytoplankton distribution showed a vertical declining trend from 0.5 m to 20 m at most sites in August 2008 (especially at sites of 1, 2, 4 and 10), but no distinct pattern in other sampling months. In December 2008 and March 2009, Stephanodiscus sp. was the most abundant species, amounting to 55.23% and 72.34%, respectively. We propose that high abundance of Stephanodiscus sp. may have contributed greatly to the frequent occurrence of Stephanodiscus sp. blooms in middle-low reaches of the Hanjiang River during the early spring of 2009. In comparison with previous studies conducted from 1992 to 2006, annual average phytoplankton density, green algae and blue-green algae species, as well as major nutrient concentrations increased, while phytoplankton diversity indices declined. This indicates a gradual decline in water quality. More research should be conducted and countermeasures taken to prevent further deterioration of water quality in the DJKR.

Reservoir-induced seismicity in the Danjiangkou Reservoir: a quantitative analysis

SUMMARY Reservoir-induced seismicity (RIS) was observed, following the impoundment in 1967 of the Danjiangkou Reservoir in Henan and Hubei provinces in central China. Starting with lowlevel seismicity, the magnitude increased with increasing lake levels, thereafter culminating in a damaging M 4.7 earthquake in 1973 November. Although the lake levels increased, the seismicity decreased. The spatial and temporal patterns of the RIS show that it was associated with through-going, deep crustal faults, especially in the vicinity of surface exposures of karsts and limestone rocks. There was a systematic increase with time of the calculated hydraulicdiffusivity(andhencethepermeability)ofthefracturesassociatedwithporepressure diffusion. Increases in lake levels over the previous highest levels were directly correlatable with increasing magnitudes of the earthquakes that followed—providing evidence of stress memory in the rocks. The seismicity was associated with increases in diffused pore pressures at hypocentral locations which ranged from < ∼100 to ∼400 kPa for M 1+ to M 4+ events.

Influence of Vegetation Characteristics on Soil Denitrification in Shoreline Wetlands of the Danjiangkou Reservoir in China

AbstractSoil denitrification in reservoir shoreline wetlands is an important process for removing excess inorganic nitrogen from upland runoff and controlling eutrophication in aquatic ecosystems. As yet, little is known about the influence of vegetation characteristics on the soil denitrification potential in reservoir shoreline wetlands, although vegetation can affect both denitrifying bacteria and soil properties. In this study, we measured the spatial variability of denitrification enzyme activity (DEA) using acetylene block method in shoreline wetlands of the Danjiangkou Reservoir, a water source of the South‐to‐North Water Transfer Project in China. Results indicated that DEA ranged from 0.001 to 2.449 µg N (N2O) g−1 h−1, with a mean of 0.384 µg N (N2O) g−1 h−1. DEA varied significantly among five representative plant communities and the highest DEA (0.248–2.449 µg N (N2O) g−1 h−1) was observed in the Polygonum hydropiper community. Plant biomass and vegetation cover were significantly and positively related to DEA and together explained 44.2% of the total variance. These results suggest that vegetation characteristics should also be considered in assessing soil denitrification capacity and restoring shoreline wetlands for nitrogen pollution removal in the Danjiangkou Reservoir after dam heightening.

Major ion chemistry and weathering processes of the Danjiangkou Reservoir, China

A total of 40 water samples were collected from five sites in the Danjiangkou Reservoir, an important drinking water source in China. Over the period November 2004–June 2006, eight field surveys were conducted and water temperature, pH, EC, major ions (Na+, K+, Ca2+, Mg2+, Cl-, and ) and Si were monitored to determine their temporal and spatial patterns across the reservoir. The controlling factors were analysed using the stoichiometry of the water chemicals and multivariate statistics including a correlation matrix and analysis of variance. The results revealed that waters in the reservoir are sub-alkaline and have a low solute load, and most water variables exhibit notable spatial and temporal variations. The major ion chemistry of the reservoir was controlled by carbonate weathering (of limestone) with the dominant ions Ca2+ and contributing 63–81% and 73–81% to the major cation and anion budgets, respectively. Carbonate dissolution was produced by both sulfuric and carbonic acids; in particular carbonic acid and silicate contributed little to the reservoir waters, while was important and originated primarily from anthropogenic inputs. This research will help water quality conservation in the Danjiankou Reservoir, China. Citation Li, S. & Zhang, Q. (2010) Major ion chemistry and weathering processes of the Danjiangkou Reservoir, China. Hydrol. Sci. J. 55(8), 1385–1395.

Phosphorus sorption and desorption characteristics of wetland soils from a subtropical reservoir

Water-level regulation results in alternating exposure and inundation of soils in reservoir fluctuation zones, which may significantly influence the phosphorus sorption and desorption processes in the soil. The present study investigated the phosphorus sorption and desorption properties of wetland soils in China's Danjiangkou Reservoir using a batch equilibrium technique. Results showed that the maximum phosphorus sorption ranged from 435 to 1429 mg kg−1, with an average of 771 mg kg−1. The maximum phosphorus sorption was found to be significantly related to amorphous iron (r = 0.883, P < 0.01) and pH (r = −0.333, P < 0.05), and the binding constant k was strongly correlated with the amorphous iron (r = 0.475, P < 0.01) and organic matter (r = −0.455, P < 0.01). The phosphorus desorption percentage varied from 8 to 44%, with a mean value of 24%. The present study implies that short-term inundation in reservoir fluctuation zones would result in soil phosphorus desorption to some extent, in spite of the considerable absorption ability in the exposure period. These results are useful for assessing the phosphorus retention capacity of wetland soils and optimising management strategies for water conservation in reservoir regions.

Phosphorus sorption and desorption characteristics of wetland soils from a subtropical reservoir

Water-level regulation results in alternating exposure and inundation of soils in reservoir fluctuation zones, which may significantly influence the phosphorus sorption and desorption processes in the soil. The present study investigated the phosphorus sorption and desorption properties of wetland soils in China's Danjiangkou Reservoir using a batch equilibrium technique. Results showed that the maximum phosphorus sorption ranged from 435 to 1429 mg kg−1, with an average of 771 mg kg−1. The maximum phosphorus sorption was found to be significantly related to amorphous iron (r = 0.883, P &lt; 0.01) and pH (r = −0.333, P &lt; 0.05), and the binding constant k was strongly correlated with the amorphous iron (r = 0.475, P &lt; 0.01) and organic matter (r = −0.455, P &lt; 0.01). The phosphorus desorption percentage varied from 8 to 44%, with a mean value of 24%. The present study implies that short-term inundation in reservoir fluctuation zones would result in soil phosphorus desorption to some extent, in spite of the considerable absorption ability in the exposure period. These results are useful for assessing the phosphorus retention capacity of wetland soils and optimising management strategies for water conservation in reservoir regions.

Spatial characterization of dissolved trace elements and heavy metals in the upper Han River (China) using multivariate statistical techniques

A data matrix (4032 observations), obtained during a 2-year monitoring period (2005–2006) from 42 sites in the upper Han River is subjected to various multivariate statistical techniques including cluster analysis, principal component analysis (PCA), factor analysis (FA), correlation analysis and analysis of variance to determine the spatial characterization of dissolved trace elements and heavy metals. Our results indicate that waters in the upper Han River are primarily polluted by Al, As, Cd, Pb, Sb and Se, and the potential pollutants include Ba, Cr, Hg, Mn and Ni. Spatial distribution of trace metals indicates the polluted sections mainly concentrate in the Danjiang, Danjiangkou Reservoir catchment and Hanzhong Plain, and the most contaminated river is in the Hanzhong Plain. Q-model clustering depends on geographical location of sampling sites and groups the 42 sampling sites into four clusters, i.e., Danjiang, Danjiangkou Reservoir region (lower catchment), upper catchment and one river in headwaters pertaining to water quality. The headwaters, Danjiang and lower catchment, and upper catchment correspond to very high polluted, moderate polluted and relatively low polluted regions, respectively. Additionally, PCA/FA and correlation analysis demonstrates that Al, Cd, Mn, Ni, Fe, Si and Sr are controlled by natural sources, whereas the other metals appear to be primarily controlled by anthropogenic origins though geogenic source contributing to them.

A fuzzy analytic hierarchy process (FAHP) approach to eco-environmental vulnerability assessment for the danjiangkou reservoir area, China

The Danjiangkou reservoir lies in the upper Hanjiang basin and is the source of water for the Middle Route Project (MRP) under the South-to-North Water Transfer Scheme (SNWT) in China. The eco-environment of water resource areas plays an important role in water conservation and purification and would have significant implications for the economic prosperity in Hanjiang basin as well as for the SNWT. Focusing on the Danjiangkou Reservoir Area (DRA), this study established an environmental information system database. Based on the database, an eco-environmental vulnerability assessment method using integrated fuzzy AHP (FAHP) and GIS was developed for the DRA. According to eco-environmental conditions and anthropic effects, vulnerability was classified into five levels: potential, light, medium, heavy and very heavy. The eco-environmental vulnerability distribution and major problems of the eco-environment were analysed and discussed. The results indicated that eco-environmental vulnerability in the DRA was moderate overall. Regions with lower eco-environmental vulnerability were located in Qinling Mountain area in the northwest, Daba Mountain area in the south and the area immediately surrounding Danjiangkou Reservoir in the east. Two regions with very high eco-environmental vulnerability were located in the north of Danjiangkou Reservoir in Henan province and in the western part of Shanxi province. On the basis of analysis of distribution of the different factors of eco-environmental vulnerability, different environmental protection measures were proposed for different areas. This study demonstrated that the proposed method was an effective approach for the assessment of environmental vulnerability. The results gained closely reflected the reality of the eco-environmental vulnerability of the DRA.

COMMUNITY STRUCTURE OF THE INTESTINAL HELMINTHS OF THE CHINESE HOOKSNOUT CARP,&lt;I&gt;OPSARIICHTHYS BIDENS&lt;/I&gt;(G-NTHER),FROM THE &lt;I&gt;DANJANGKOU RESERVIOR&lt;/I&gt;

Many parasite community structures in fish have been demonstrated non-random but the results were not consistent at any time. Some environmental factors and host traits are likely to influence the parasite community structure. Here, we address this question using data on the intestinal helminthes community of the Chinese hooksnout carp Opsariichthys bidens from the Danjiangkou Reservoir, China, and focus on the impactions caused by host body length and season variation.During the time from February 2004 to November 2005 848 specimens of O. bidens were collected and examined. In total, 14 species of the intestinal helminths were found: 7 nematodes,4 digeneans,2 acanthocephalans and I cestode. The result showed that 87.49% of O. bidens were parasitized by at least one parasite species and the mean intensity was 8.71 +/- 11.557. The mean infracommunity diversity was Brillouin index = 0.238 +/- 0.287. The infracommunity diversity showed significantly positive correlation with host's total length ( Spearman rank correlation coeffection r, = 0.09 p 0.05). The nematodes Carnallanus cotti and Rhabdochona cascadilla, the cestode Bothriocephalus acheilognathi, and the acanthocephalan Micracanthorhynchina motomurai with higher prevalence and intensity were the core species of this community. The infection intensities of the core species were significantly correlated with the host's body length (r, = 0.238, -0.159, 0.150, -0.115;p = 18 cm respectively, showed that the changes of diet and body length of the host had significant impact. The parasite community in host with longer body length inclined to have significantly interspecific correlation. Also the parasite community in summer and autumn show the same tendency.

Spatial and temporal patterns of the water quality in the Danjiangkou Reservoir, China

The three-route South-to-North Water Diversion Project (SNWDP), transferring water from the water-rich Yangtze River and its tributaries to the much drier area of North China for irrigation, industrial and domestic use, has been implemented in China since 2002. Thus, water quality in the Danjiangkou Reservoir, the water source area of the SNWDP's Middle Route, is of great concern. We investigate its water quality from 2004 to 2006 by monitoring some important physical (T, turbidity and SPM) and chemical (DO, pH, alkalinity, TDS, SpCond, ORP, CODMn and BOD) parameters and nutrient (nitrogen and phosphorus) contents. Consequently, their spatial and temporal patterns in the reservoir were examined. The results indicate that the water of the reservoir is of a Ca and HCO3 type, and the major pollutants are nitrogen and CODMn. Comparisons among the sampling sites show that water quality increases downstream, implying the self-purification capacity of the reservoir. The reservoir in general has better water quality in the dry season than in the wet season. Integrated basin management would be critical of the water quality in the Danjingkou Reservoir for the interbasin water transfer project.

Non-uniform sediment transport downstream from reservoir

The transport characters of non-uniform sediment before and after the reservoir operation are compared and analyzed. Field data from the Three Gorges Reservoir (TGR), Danjiangkou, and Sanmenxia reservoir indicate that the transport character of coarse particle is various in different reaches. Before the reservoir operation, the dramatic decrease of the hydraulic condition in some reaches is the main reason to cause the coarse particle deposited. After the reservoir operation, almost all grain sized sediment may be eroded, when the reach is eroded seriously. However, the transport character of the coarse particle will be consistent with what it was before, when the reach is not eroded seriously. The deposition amount will be less than its pre-dam value, and it will tend to decrease with the time going on. Erosion of fine particle results from its unsaturation. Long-distance erosion downstream from reservoir is caused by shortage of the supply from riverbed, especially the shortage of fine particle.

Seed banks of a river–reservoir wetland system and their implications for vegetation development

The Danjiangkou Reservoir, constructed in 1970s, is the water source area of the middle route of China's interbasin South-to-North Water Transfer Project. To serve such purpose, the Danjiangkou Reservoir Dam will be increased from its present 162.0 m to 176.6 m, and its regular water level from 157 m to 170 m above mean sea level. Vegetation development in the new reservoir margins is therefore one of great environmental concerns. To explore the potential origin of species in the present reservoir margin vegetation, we investigated and quantified the composition in the soil seed banks and established vegetations of the reservoir margins and its upstream- and downstream-wetlands. In both existent vegetation and seed banks, most species and seedlings were found in upstream wetlands, followed by reservoir margins and downstream wetlands. Seedling density of downstream wetlands was reduced by 75–80% compared to upstream wetlands and reservoir margins. This suggests that presence of the dam reduced the diversity and abundance of downstream propagules. Sørensen's coefficient and the comparisons of rare species indicated that the seed bank composition of reservoir margins was evidently associated with upstream wetlands. It implies that hydrochorous transport of seeds from the upstream catchment is critical for plant colonization of the reservoir margins.

A New Species of Allocreadium (Trematoda: Allocreadiidae) from Freshwater Fishes in the Danjiangkou Reservoir in China

A new species of Allocreadium, Allocreadium danjiangensis n. sp., is described from the intestine of several species of freshwater fish, including Abbottina rivularis (Basilewsky, 1855), Sarcocheilichthys nigripinnis nigripinns (Güther, 1873), Gnathopogon argentatus (Sauvage et Dabry 1874), Opsariichthys uncirostris bidens (Gunther, 1873), and Erythroculter mongolicus mongolicus (Basilewsky, 1855) (Cyprinidae) from the Danjiangkou Reservoir in central China. The main morphological characters of the new species are as follows: vitelline follicles numerous, extending from the level of acetabulum to posterior extremity, distributed over both sides around the ceca; cirrus sac relatively large, developed, lying obliquely anterior to the acetabulum, extending from the level of the intestinal bifurcation to the central level of acetabulum, and overlapping left or right cecal; and ovary much smaller than testes, generally close to or even overlapping the anterior border of anterior testis. Observation by scanning electron microscopy shows only 2 kinds of tegumental formations, i.e., papillae and tubercles, instead of 3 types of tegumental formations, i.e., papillae, bosses, and minute sensor receptors observed on other species of the Allocreadiidae. The tegumental striations of the present species vary on the different parts of the body. In addition, a new structure, identified as the "groove" with a tonguelike tubercle, was observed on the inner wall of acetabulum.

Using MODIS images to examine the surface extents and variations derived from the DEM and laser altimeter data in the Danjiangkou Reservoir, China

We used publicly available digital spatial datasets to study the area extents and their horizontal variations of two water bodies within the Danjiangkou Reservoir, China. Between 2003 and 2005, the water levels varied from 140 to 149 m above mean sea level as measured by the Geoscience Laser Altimeter System (GLAS). Detailed procedures to derive the horizontal extents and variations from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) coupled with GLAS data and to verify the extents and variations spatially were provided. For the water bodies on the north and west, the surface water extents derived from four MODIS images varied between 174 and 218 km2 and from 96 to 135 km2, respectively. The extents by inundating the DEM using the GLAS data were 178–212 km2 for the water body on the north and 104–118 km2 for the water body on the west. The spatial verifications of surface water extents derived from the MODIS images versus DEM coupled with GLAS data agreed 83–93%. Within the ring areas between water/land boundaries at elevations of 140 and 147 m, and 140 and 149 m, the spatial agreement was 52–75%.

Dissolved trace elements and heavy metals in the Danjiangkou Reservoir, China

Concentrations of trace elements and heavy metals (Al, As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sb, Se, Sr, V and Zn) in the Danjiangkou Reservoir, the water source area of the Middle Route of China’s interbasin South to North Water Transfer Project, were analyzed using an Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES) and compared with the national and international standards for drinking water. The results indicated that concentrations of As, Pb, Sb and Se in the Reservoir exceeded the standards and they would pose health risk for residents in the region and the water receiving areas of the interbasin water transfer project. Spatial and temporal variability of the trace elements and heavy metals in the Reservoir implies their mixed sources of natural processing and anthropogenic activities in the upper drainage of the Reservoir. The research results would help develop water resource management and conservation strategy for the interbasin water transfer project.

Historical temporal trends of hydro-climatic variables and runoff response to climate variability and their relevance in water resource management in the Hanjiang basin

The Danjiangkou reservoir lies in the upper Hanjiang basin and is the source of water for the middle route of the South-to-North Water Diversion Project (SNWDP) in China. Any significant change in the magnitude or timing of runoff from the Danjiangkou reservoir induced by changes in climatic variables would have significant implications for the economic prosperity of the area in the Hanjiang basin as well as for the South-to-North Water Diversion Project. In this paper the following issues are investigated: (1) Temporal trends of annual and seasonal precipitation and temperature from 1951 to 2003 in the Hanjiang basin are analyzed using the Mann–Kendall and the linear regression methods; spatial distributions of precipitation and temperature are interpolated by the inverse distance weighted interpolation method. (2) Temporal trends of runoff, precipitation and temperature from 1951 to 2003 in the Danjiangkou reservoir, an upper stream basin of the Hanjiang River, are further tested. (3) To assess the impact of climate change on water resources and predict the future runoff change in the Danjiangkou reservoir basin, a two-parameter water balance model is used to simulate the hydrological response for the climate change predicted by GCMs for the region for the period of 2021–2050. The results indicate that (1) at the α = 0.05 significance level precipitation in the Hanjiang basin has no trend, but the temperature in the same region has significant upward trends in most parts of the Hanjiang basin. (2) The mean annual, spring, and winter runoffs in the Danjiangkou reservoir basin have decreasing trends. (3) The results simulated for the period 2021–2050 show that runoff of the Danjiangkou reservoir would increase in all the seasons, mainly in response to the predicted precipitation increase in the region. Sensitivity analysis shows that a 1 °C and 2 °C increase in temperature would reduce the mean annual runoff to about 3.5% and 7%, respectively. A decrease/increase of the mean monthly precipitation of 20% and 10% would decrease/increase the mean annual runoff to about 30% and 15%, respectively. The results of this study provide a scientific reference not only for assessing the impact of the climate change on water resources and the flood prevention in the Hanjiang basin, but also for dimensioning the middle route of the SNWDP in China.

Population dynamics and maturation cycle of Camallanus cotti (Nematoda: Camallanidae) in the Chinese hooksnout carp Opsariichthys bidens (Osteichthyes: Cyprinidae) from a reservoir in China

The seasonal population dynamics and maturation cycle of the nematode Camallanus cotti in the posterior intestine of Chinese hooksnout carp Opsariichthys bidens have been studied in the Danjiangkou Reservoir of the Hubei Province in central China from September 2004 to November 2005. The overall prevalence, mean abundance and intensity of C. cotti among fish sampled ( n = 700 fish) were 47%, 2.29 ± 12.38 (±S.D.) and 1–307 (average 4.89 ± 17.74), respectively. The overall sexual ratio of female to male nematodes (excluding L3 and L4 juveniles) was 1.17:1. Statistical results showed weakly positive correlations between fish length and the number of nematodes per host. The dynamics of infection of the nematode exhibited significant seasonal pattern in changes in mean abundance. A similar pattern was found for changes in nematode prevalence, although this was not statistically significant. Higher levels of infection were observed among fish sampled in summer months and the lower in the winter. Neither the prevalence nor the abundance of the parasite was significantly different between male and female hosts. The pattern of frequency distribution of the parasite in the host was found to be over-dispersed throughout the sampling period. In addition, studies on the development and maturation of the parasite in O. bidens revealed that development (maturation), recruitment of the next generation, and reproduction may be continuous year-round, although reproduction may peak during the winter.

Occurrence of Camallanus cotti in greatly diverse fish species from Danjiangkou Reservoir in central China

Two thousand four hundred fifty-eight fish comprised of 53 species were captured in the Danjiangkou Reservoir, in the northwestern part of Hubei Province, central China during 2004, to examine Camallanus cotti infections. We found that 19 cypriniform, 3 siluriforme, and 4 perciforme fishes were infected by the nematode. Our study revealed the species, Hemiculter bleekeri bleekeri, Culter oxycephaloide, Pseudolaubuca sinensis, Acanthobrama simony, Mylopharyngodon piceus, Ctenopharyngodon idella, Gnathopogon imberbis, G. argentatus, Saurogobio dabryi, S. dumerili, Gobiobotia ichangensis, Liobagrus marginatoides, and Ctenogobius shennongensis as new hosts of the worm. The number and range of fish host species found in this survey were much greater than any of the previous investigations. The mean prevalence, prevalence, mean abundance, and intensity of infection varied in different fish species, indicating a possible host preference. Moreover, we suggest that this nematode is a native parasite of cypriniform fishes in China, perhaps initially in the reaches of the Yangtze River.

Dam impacts on the Changjiang (Yangtze) River sediment discharge to the sea: The past 55 years and after the Three Gorges Dam

In 5 recent years (2000–2004), the Changjiang (Yangtze) River has discharged past Datong (600 km from the river mouth) an average of ∼250 million tons (mt) of sediment per year, a decrease of more than 40% since the 1950s and 1960s, whereas water discharge at Datong has increased slightly. Water and sediment discharge data from the upper, middle, and lower reaches of the river suggest that the reduction of the Changjiang sediment load has occurred in two phases between 1950 and 2002: following the closure of the Danjiangkou Reservoir on the Hanjiang tributary in 1968 and following the installation of numerous dams and water‐soil conservation works in the Jialingjijang catchment after 1985. As the Three Gorges Dam (TGD) started operating in 2003, the Changjiang entered a third phase of sediment reduction with annual sediment loads at Datong less than 200 mt/yr. Upon completion of the Three Gorges Dam (TGD) in 2009, the sediment load at Datong will decrease to ∼210 mt/yr for the first 20 years, then will recover to ∼230 mt/yr during 2030–2060, and will reach ∼310 mt/yr during 2060–2110. From the sediment budget and sediment erosion data for the Changjiang subaqueous delta, it can be assumed that the delta will be eroded extensively during the first five decades after TGD operation and then will approach a balance during the next five decades as sediment discharging from TGD again increases.

Water chemistry and water quality variation in the Danjiangkou Reservoir, as a function of water management for the Middle Route of South to North Water Divert Project, China

Water chemistry and water quality variation in the Danjiangkou Reservoir, as a function of water management for the Middle Route of South to North Water Divert Project, China