WATER QUALITY IN SPRINGS, CANALS, AND WELLS AT LIJIANG, YUNNAN PROVINCE, CHINA

Springs emerging from Permian-Triassic limestones provide the historic water supply for the old city of Lijiang, where about 30,000 people presently reside in an area of 3.8 km² without modern plumbing or water treatment. Primary spring water is distributed in a network of canals. Smaller springs supply additional water within the city. In recent decades, shallow (e.g., 2 m) wells with hand pumps were emplaced in alluvium to augment water supply at individual urban residences, and a small diameter pipe was laid to supply water from primary springs to parts of the city. To investigate relations between spring, canal, and well waters, and to make a reconnaissance evaluation of water quality, forty water samples were collected in July 2002 and analyzed for T, pH, Eh, NO₃^-, Cl^-, and Na⁺. T, pH, and Eh varied over narrow ranges (15 – 18°C, 7.0 – 8.3, and 350 – 500 mV). Concentrations of Cl^- and NO₃^- were below 1.5 mM, Na⁺ was below 2.5 mM, and concentrations of these constituents were generally correlated. Water in primary springs and canals had low Cl^- (< 0.1 mM), NO₃^- (< 0.1 mM), and Na⁺ (< 0.3 mM), and elevated pH (> 7.7). Na⁺, Cl^-, and NO₃^- in canal waters increased and pH decreased with distance from primary springs. Inner-city springs occur mainly along the course of the central canal and showed no clear trends in chemistry with location. Shallow wells and inner-city springs had chemically similar waters and had a broader range of higher concentrations than canal waters. Waters from shallow wells and inner-city springs can be subdivided in three groups. Three wells and one spring with high Cl^- and NO₃^- occur in an east-west band across the central city. Three high Cl^- and low NO₃^- wells occur in the northern (upstream) part of the city. Low Cl^- and NO₃^- wells and springs occur in a band in the southern part of the city. Two deep wells for modern hotels at the downstream margin of the old city had low concentrations of NO₃^-, low Eh, and low Na⁺/Cl^- ratios compared to shallow well waters. Although water quality in primary springs and canals appears good on the basis of data collected in this survey, local or transient canal pollution is indicated by one exceptional sample with pH of 10.7; and elevated NO₃^- in several shallow wells and one inner-city spring is of concern with regard to routine human consumption.