‘Aihualama Stream is a very small stream (we even can’t see the stream from google map). In normal days, the stream width is less than 3 m (9.84 ft) with mean discharge 0.021/0.74 cubic meter per second/cubic feet per second (cms/cfs). With mean daily rainfall, 10.7 mm (0.42 inches), the mean discharge of the Mississippi rever is 16791.8 cms (593000 cfs). [Note: the rainfall data is from NOAA’s National Climatic Data Center (NCDC); the data of ‘Aihualama Stream is from Tsang Hydrology Lab]
Although ‘Aihualama is small, don’t ignore the power of our mother nature! The streamflow can increase rapidly during a rainfall event (the discharge can hit 20 times of normal discharge during hours!!! So be careful while you’re hiking on a rainy day in Hawaii!!!). The first figure below is showing the stream on a normal day, and water can reach the orange lines during a rainfall event. As Oki (2003) pointed out, Hawaiian streams are very flashy, ‘Aihualama is not excluded (see the second picture below)
So, who lives in this extreme flow amount stream? I guess the stream animals must have the ability to hide or hold tightly on the bottom that they won’t be flush away from a high, fast and turbulent flow. Besides, they have to tolerate the small amount of stream flow, which may cause the larger fluctuate in temperature, discontinuous stream and smaller habitat.
I saw a lot of small suckermouth armored catfishes in pools (not showing here), and crayfishes (the first photo below), guppies along the entire stream. They’re considered as invasive species for Hawai’i; they occupied the stream, and some of them eat the native species’ eggs (Devick 1989) . Also, there is an argument saying invasive fishes would impact the nutrient content and water quality in streams (Nico 2006; Capps et al. 2009)
Did I only see invasive fishes in ‘Aihualama stream? Well, I still see one or two o’opu (as the second photo), Hawaiian native goby, in the pool within like more than 30 catfishes…
On the stream bank, I saw a green and black poison dart frog (Dendrobates auratus) (the third photo below), this small tree frog is native to Central and South America. As their name implies, blow darts were rubbed on the back of frogs by indigenous tribes to make poison-tipped darts. They were introduced to Manoa Valley in the 1950s to control mosquitoes; however I didn’t find any evaluation for its consequence. More and more…. I ALWAYS GOT MOSQUITO BITTEN every time I went there…
Black small mushrooms (?) on a dead wood across the ‘Aihualama stream… I don’t know the name of the mushrooms, but it smelled not good…
On the right bank of ‘Aihualama stream at Lyon Arboretum, there are lo’i (taro farm; the first picture below), which is a part of Hawaiian cultural practicing. Some people and students go there every Wednesday to plant kalo (taro). For the farming, they need to divert the stream water into their farms, thus they use pipes (the second and third photo below) to divert the stream water into their lo’i. Most of the streams in Hawaiian are diverted for agriculture purpose; however, the water issues and conflicts increased during and after the sugar cane and pineapple plantations. How we manage the water resources and communicate with our friends living together are big challenges for us…
Capps, K.A. and Flecker, A.S., 2013, October. Invasive aquarium fish transform ecosystem nutrient dynamics. In Proc. R. Soc. B (Vol. 280, No. 1769, p. 20131520). The Royal Society.
Devick, W.S., 1989. Disturbances and fluctuations in the Wahiawa Reservoir ecosystem. Honolulu: Hawaii Department of Land and Natural Resources, Division of Aquatic Resources.
Nico, L., Fuller, P., Cannister, M. and Neilson, M., 2006. Pterygoplichthys disjunctivus. USGS Nonindigenous Aquatic Species Database, Gainesville, FL. Revision Date, 4(21), p.2006.
Oki, D.S., 2003. Surface water in Hawaii. US Department of the Interior, US Geological Survey.
(All the photo in this post were taken by Yu-Fen Huang/yfhuang)
The “shaka sloth” I met along the stream! 😀