Overview of the Surface Hydrology of Hawai i Watersheds Ali Fares Associate Professor of Hydrology NREM-CTAHR 5/23/2008 Watershed Hydrology Lab 1
What is Hydrology? Hydrology is the water science that is concerned with the origin, circulation, distribution and properties of water. There are different branches of hydrology, i.e., surface hydrology, groundwater hydrology, subsurface hydrology, etc 5/23/2008 Watershed Hydrology Lab 2
Water Cycle 5/23/2008 Watershed Hydrology Lab 3
What is surface hydrology? Surface hydrology is the branch of hydrology dealing with surface water Surface Water is water that is on the Earth's surface, such as in a stream, lake, or reservoir. 5/23/2008 Watershed Hydrology Lab 4
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Stream flow separation 60 50 Total flow Baseflow Streamflow (m -3 s) 40 30 20 10 0 1/1/03 5/1/03 8/29/03 12/27/03 4/25/04 8/23/04 12/21/04 Base flow and direct runoff were 62% 38% of total stream flow, respectively. 5/23/2008 Watershed Hydrology Lab. 6
Geology of Hawaii Hawaiian island chain consist of one or more shield volcanoes which are primarily composed of extremely permeable, thin basaltic lava flows. 5/23/2008 Watershed Hydrology Lab 7
Intermittent stream hydrology Dike impounded system 5/23/2008 Watershed Hydrology Lab 8
Natural Stream & Ditch Systems 5/23/2008 Watershed Hydrology Lab 9
Effect of Spatio-temporal variation of Rain at the Island and Watershed Scales 5/23/2008 Watershed Hydrology Lab 10
Orographic Precipitation 5/23/2008 Watershed Hydrology Lab 11
Elevation and Rain Distribution 5/23/2008 Watershed Hydrology Lab. 12
Spatial rain-runoff variability 5/23/2008 Watershed Hydrology Lab 13
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Rainfall variability: monthly total 5/23/2008 Watershed Hydrology Lab 15
Rainfall variability: monthly total Ewa (leeward) Koolau (windward) 5/23/2008 Watershed Hydrology Lab 16
Runoff variability: monthly stream discharge 5/23/2008 Watershed Hydrology Lab 17
Runoff variability: instantaneous stream discharge 5/23/2008 Watershed Hydrology Lab 18
Rain, and Total & Base Flow, Makaha Total Flow Base Flow Rainfall 50 0 45 2 40 35 30 25 20 15 4 6 8 10 10 5 0 1/1/03 2/1/03 3/1/03 4/1/03 5/1/03 6/1/03 7/1/03 8/1/03 9/1/03 10/1/03 11/1/03 12/1/03 1/1/04 2/1/04 3/1/04 4/1/04 5/1/04 6/1/04 7/1/04 8/1/04 9/1/04 Total Flow and Base Flow(cfs) Rainfall(in) 12 14 Time(day) 5/23/2008 Watershed Hydrology Lab 19
Rain, and Total & Base Flow, Hanalei Total Flow Base Flow Rainfall (in) 3000 0 2750 2500 5 2250 2000 1750 1500 1250 1000 750 10 15 20 500 250 0 1/1/03 2/1/03 3/1/03 4/1/03 5/1/03 6/1/03 7/1/03 8/1/03 9/1/03 10/1/03 11/1/03 12/1/03 1/1/04 2/1/04 3/1/04 4/1/04 5/1/04 6/1/04 7/1/04 8/1/04 9/1/04 10/1/04 11/1/04 12/1/04 Total Flow and Base Flow for Hanalei(cfs) Rainfall (inch) 25 30 Time(day) 5/23/2008 Watershed Hydrology Lab 20
Rain- Overland Flow, Makaha Strm Netflow Poly. (Netflow) 60.00 50.00 y = 13.038x 2 + 1.1038x - 0.0263 R 2 = 0.8242 40.00 Netflow(cfs) 30.00 20.00 10.00 0.00 0.00 0.50 1.00 1.50 2.00 Rainfall(in) 5/23/2008 Watershed Hydrology Lab 21
Rain-Overland Flow, Hanalei Strm Netflow Poly. (Netflow) 700 y = 86.009x 2 + 210.41x + 0.6111 R 2 = 0.6955 600 500 Netflow(cfs) 400 300 200 100 0 0.00 0.50 1.00 1.50 2.00 Rainfall(in) 5/23/2008 Watershed Hydrology Lab 22
Long-Term Trends of Stream Flow in Hawaii 5/23/2008 Watershed Hydrology Lab 23
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Trends in Streamflow Characteristics in HI 5/23/2008 Watershed Hydrology Lab 25
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USGS stream-gaging stations in HI 5/23/2008 Watershed Hydrology Lab 27
Case study: Makaha valley hydrology Evaluation of the Effects of Alien Plant Species, Groundwater Extraction, and Long-term Weather Patterns on Mākaha Valley s Stream Flow O'ahu Mākaha Valley 5/23/2008 Watershed Hydrology Lab 28
Case study: Makaha valley hydrology Objectives Produce detailed vegetation maps (Miura) Assess spatial-temporal variation of hydrologic cycle Calibrate and validate a watershed model Evaluate effect(s) of changing vegetation, weather patterns, and groundwater pumping 5/23/2008 Watershed Hydrology Lab 29
Case study: Makaha valley hydrology Long term observed data Streamflow-Rainfall-Pumping 3000 1600 Rainfall (mm) 2500 2000 1500 1000 1400 1200 1000 800 600 400 Streamflow & Groundwater Pumping (mm) 500 200 0 0 2003 2001 1999 1997 1995 1993 1991 1989 1987 1985 1983 1981 1979 1977 1975 1973 1971 1969 1967 1965 1963 1961 1959 Water Year (Oct - Sept) 5/23/2008 Watershed Hydrology Lab 30
350 300 250 Case study: Makaha valley hydrology Long term observed data Dry Stream Conditions Pre-Pumping Pre-Pumping (1959-1989) Ave Streamflow = 322 mm Ave Rainfall = 1899 mm Ave Dry Stream = 8 days Pumping Dry Stream (days/year) 200 150 100 Pumping (1990-2003) Ave Streamflow = 181 mm Ave Rainfall = 1641 mm Ave Dry Stream = 127 days Ave Pumping = 130 mm 50 0 1959 1961 1963 1965 1967 1969 1971 1973 1975 1977 1979 5/23/2008 Watershed Hydrology Year (Oct - Sept) Lab 31 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003
Case study: Makaha valley hydrology Hypotheses for Streamflow Reduction 1. Caused by reduction in rainfall. 2. Caused by increases in evapotranspiration due to: 1. atmospheric demand. 2. changes in vegetation. 3. Caused by pumping of groundwater. 4. Caused by a combination of two or more of the above. 5/23/2008 Watershed Hydrology Lab 32
Case study: Makaha valley hydrology 5/23/2008 Watershed Hydrology Lab 33
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Case study: Makaha valley hydrology Station Configuration Rainfall Rain gage/ weather station Soil moisture sensors 5/23/2008 Watershed Hydrology Lab 35
10 2.5 9 8 2.0 7 Rainfall (mm/day) 6 5 4 1.5 1.0 Streamflow (mm/day) 3 2 0.5 1 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Rain Gage 844 Rain Gage 842.1 Stream Gage 2116 0.0 5/23/2008 Watershed Hydrology Lab 36
Rainfall Spatial Distribution 350 300 250 Gross Precipitation (mm) 200 150 100 50 0 Aug 2005 Sep 2005 Oct 2005 Oct 2006 842.1 1 2 3 4 5 6 844 5/23/2008 Watershed Hydrology Lab 37
Pre-Post Pumping Rainfall 2200 2000 1800 a 1600 Mean Gross Precipitation (mm) 1400 1200 1000 800 600 400 200 0 842.1 844 Pre Post 5/23/2008 Watershed Hydrology Lab 38
Effect of rainfall spatial distribution on surface water and sediment 5/23/2008 Watershed Hydrology Lab. 39
Scenario 1 PRIZM model Scenario 2 Giambelluca, 1986 5/23/2008 Watershed Hydrology Lab. 40
Introduction - Objectives - Methods - RESULTS - Conclusions Resulting spatial distribution of runoff Scenario 1 Scenario 2 5/23/2008 Watershed Hydrology Lab. 41
Resulting spatial distribution of sediment yield Scenario 1 Scenario 2 5/23/2008 Watershed Hydrology Lab. 42
Multidisciplinary Approach! 5/23/2008 Watershed Hydrology Lab 43
Additional Readings 5/23/2008 Watershed Hydrology Lab 44
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Urbanization effects 5/23/2008 NREM 662 Watershed Hydrology Fall 05 48
Rainfall-Runoff: CN Method Q = runoff, P = rain, S = potential maximum retention after runoff begins (in) and Ia = initial abstraction = 0.2*S Q = (P 0.2* S) (P + 0.8* S) 1000 S = 10 CN 2
What s a Watershed? WATERSHED, or CATCHMENT, is a topographic area that is drained by a stream, that is, the total land area above some point on a stream or river that drains past that point. The watershed is often used as a planning or management unit. Natural environment unit. 5/23/2008 Watershed Hydrology Lab 51
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Oahu s Watersheds 5/23/2008 Watershed Hydrology Lab 53