Fig. 8. Estimation of baseflow NO₃^– concentrations for 1960 to 2050. (a) Lines A, B, and C, projected basin-wide mean annual concentration in ground water recharge (total NO₃^–) scenarios, extended into the past (1920) and future (2050) sufficiently to generate baseflow concentration (C_bf) predictions between 1960 and 2050. Scenarios are described in the text. See Fig. 7a for explanation of vertical point diagram. (b) Lines A', B', C' are corresponding C_bf estimates. Shaded area in A' represents C_bf (excess N₂). Cross-hair represents year 2000. (c) C_bf (±SD) values (solid circles) from the lower left quadrant (1960 to 2000) in Fig. 8b are superimposed on historical baseflow NO₃^– measurements (small open circles). Solid line: best fit historical data (slope = 0.152 mg L^–1 yr^–1). Dashed line: best fit C_bf backcasts (slope = 0.159 mg L^–1 yr^–1).