The relationships between carbon isotope discrimination (?) and some morphophysiological traits such as specific leaf dry weight (SLDW), gas exchange parameters, and relative water content (RWC) were studied in a collection of 20 bread wheat cultivars (landraces, released cultivars and advanced lines) in three locations of the Ningxia region (North-East China), i.e. Yinchuan (limited irrigation conditions), Huinong (limited irrigation conditions + salinity) and Guyuan (rain-fed conditions). Relationships between Δ, grain yield (GY), and harvest index (HI) and above-ground biomass (AGB) were also analysed. Differences in the measured traits between different locations were highly related to the variation in water availability. Positive correlations were noted between Δ and HI and grain yield. Flag leaf Δ was positively correlated with RWC at anthesis, and negatively associated with SLDW at grain filling. Significant and negative correlations between Δ and dry matter weight per plant at anthesis and biomass at maturity were noted. Leaf temperature (LT) was found to be negatively correlated with ? and gs. The findings suggest that ? may be a useful indicator reflecting wheat yield, harvest index, and water status under irrigation and rain-fed conditions in the Ningxia region.