Results and discussion
Above computation gives 50-year of synthetic rainfall and temperature data , evapotranspiration coefficient, CET, on 2xCO2 condition, and other model parameters. Daily runoff are simulated to calculate flow-duration-curves (FDC) for assessing the runoff frequencies of both 1xCO₂ and 2xCO₂ conditions. Fig. 5 illustrates the FDCs of Fusan basin. Table 4 and Fig 6 summarize the flow change rates. Results show that frequencies of low flow are decreased in Fusan and Lisan basins. Q₉₀ are down to 57% and 49% of original values. However, high flows, Q₁₀ , are increase to 165% and 187%, respectively. It shows high possibility of appearing a peak flow on flood period..
Table 4. Flow rate changes of two climate conditions (Q_2xCO2 / Q_1xCO2)

Exceed Possibility	Fusan	Chichiawan	Sandiman	Lisan
90%	57%	108%	163%	49%
80%	58%	105%	223%	58%
70%	63%	110%	331%	71%
60%	70%	109%	431%	86%
50%	82%	102%	498%	103%
40%	98%	106%	344%	124%
30%	118%	111%	271%	144%
20%	137%	130%	242%	169%
10%	165%	162%	228%	187%

Fig.5 Flow duration curve of Fusan



Fig.6 Flow change rate of four basins

Lisan and Sandiman basins have increasing values in both low and high flows. Though Sandiman locates on tropical southern-Taiwan, higher temperature doesn’t evaporate the extra rainfall supply during drought period. Comparing mean flows, Q₅₀, of the four basins, Chichiawan and Lisan show insignificant change. Fusan reduces to 82% of original condition, while Sandiman on the south has five times of original flow. Southern region has very low mean flow on present condition that may cause this significant increase. Table 5 shows the ratio comparing flows of different possibilities from 1xCO₂ and 2xCO₂ conditions. Sandiman shows higher values on Q₅₀/Q₉₀ and Q₁₀/Q₅₀. 2xCO₂ condition introduces increase rate of Q₅₀ that makes an improvement of non-uniform timely distribution on southern region.
Table 5 Ratio of flow of different exceed possibilities of the four studied basins

Flow Ratio	Fusan		Chichiawan		Sandiman		Lisan
	1 xCO2	2 xCO2	1 xCO2	2 xCO2	1 xCO2	2 xCO2	1 xCO2	2 xCO2
Q 50/Q90	1.90	2.72	2.56	2.41	3.46	10.54	1.72	3.59
Q10/Q50	2.57	5.20	3.43	5.46	27.29	12.49	3.30	6.00

Conclusion
The study combines rainfall-runoff model, vegetation index defined by remote sensing, output of GCM , and data disaggreation model to estimate the changed evapotranspiration parameter for calculating runoff of four basins located on north, middle, south, and east regions. Flow duration curves is calculated to assess the impact of runoff from climate change. Results show that:

• Fusan (north region) and Lisan (east region) show larger flood and smaller drought flow. Increasing rainfall and warmer weather brings double impact to the two basins. Chichiawan (middle region) shows insignificant changes on flood but smaller drought flow.
• Sandiman (south region) has significant increase flow rate at all exceeded probabilities. A five-time high of average flow provides positive contribution for water resource planning.
• High flow, Q₁₀, are increase in all four basins, and the Sandiman basin makes a highest value of 228% that makes negative impact on flood control.

Reference

• Hun, Lan-Min, Chin-Pin Tung, "Affection of Climate-Change to Taiwan’s Hydrology,” Proceeding, Conference of Agricultural Engineering, Taipei, pp.683-690(1996).
• Houerou, H. N. Le, “Vegetation and Land-Use in the Mediterranean Basin by the Year 2050: A Prosectire Study” in Climate Change and the Mediterranean (L. Jeftic Edited), Edward Arnold, London, pp.175~232. (1992).
• Lau, Chi-Chung, ”Assessment of Climate-Change Impact on Hydrologic System of Taiwan using Remote Sensing (I),”, ERL/ITRI report 06-3-85-0176, Hsinchu (1995).
• Shoshany, M., P. Kutiel, H. Lavee and M. Eichler, “Remote Sensing of Vegetation Cover along a Climatological Gradient,” ISPRS. Journal of Photogrametry and Remote Sensing, Vol.49,No.4,pp.2-10(1994).
• Skiles, J. W. and J. D. Hanson, “Responses of Arid and Semiarid Watersheds to increasing Carbon Diexide and Climate Change as Shown by Simulations Studies,” Climate Change, Vol.26, pp.377-397,(1994).
• Tung, Chin-Pin, Douglas A.Haith.”Weather-form Classification and Precipitation Simulation Model,” Proceeding, Conference of Agricultural Engineering, Taipei, pp.167-182(1995).