Study of the Runoff Depth and Its Processes of Eucalyptus Plantations Natural Watersheds

Abstract

The runoff and runoff process of <i>Eucalyptus</i> plantations natural watersheds were studied to provide guidance for scientific evaluation of water conservation capacities of <i>Eucalyptus</i> plantations, compared with the <i>Pinus massoniana</i> forest natural watersheds. The runoff volume of <i>Eucalyptus</i> plantations and <i>P. massoniana</i> forest natural watersheds were continuously monitored using the small watershed runoff monitoring method and the automatic data collection devices from August, 2013 to December, 2015, and effects of heavy rainfall and continuous rainfall on the runoff process were studied. Results show that the annual runoff coefficient of <i>Eucalyptus</i> plantations natural watershed were 0.046, and 55.8% lower than <i>P. massoniana</i> forest (0.104), with the difference being significant (P&lt;0.01). The runoff duration, time lags, maximum runoff of rainfall, and runoff depth amounts caused by a heavy rainfall process (amounting to 65.5 mm) between the two kinds of forest watershed were significant different, those of <i>Eucalyptus</i> plantations were 8.5 h, 25 min and 2.69 mm, respectively, while those of <i>P. massoniana</i> forest were 18.4 h, 55 min and 5.52 mm, respectively. <i>Eucalyptus</i> plantations natural watershed produced only 4-days runoff, and runoff depth amounted to 3.8 mm with a 7 days continuous precipitation process of rainfall with 125.0 mm, while <i>P. massoniana</i> forest produced continuously 13-days runoff, and the runoff depth was 10.1 mm. In conclusion, water conservation capacity of <i>Eucalyptus</i> plantations is obviously lower than <i>P. massoniana</i> forest.