Hillslope Hydrology Final Thesis Fisnu L4A 009 016

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2.3.2 Non-Groundwater Basin

Geologically, non-groundwater basin is generally in the form of impermeable rock with a layer of thin soil on top Kodoatie Sjarief, 2010. Groundwater basin is area underlain by permeable materials. The material is capable of furnishing a significant availability of groundwater to wells or storage a significant amount of water California Department of Water Resources, 2003, so non-groundwater basin is area which has underlying impermeable material such as impermeable bedrock, clay etc. Referring to the definition of groundwater basin, non-groundwater basin are the area which have no hydrogeological boundaries and it is not a place for hydrological process such as recharge, discharge, drainage and baseflow. Non-groundwater basin Kodoatie Sjarief, 2010 are also the region that:  Does not has a hydrogeological boundary.  Does not has recharge and discharge area of groundwater in a single groundwater formation system.  It is not a single aquifer system. When forest or vegetation covered the area of non-groundwater basin, the forests or vegetation will maintain the soil layer naturally. In non-groundwater basin, the water in the top soil layer as a source of plant life has more volume than in groundwater basin area, so under natural conditions, forests or vegetations in the area of non-groundwater basin are more fertile than in the groundwater basin because in the groundwater basin, water can seep up to hundreds of meters below the soil surface percolation. This is the way the local natural conditions in non- groundwater basin area is relatively more fertile than in the groundwater basin Kodoatie Sjarief, 2010.

2.4 Hillslope Hydrology

A raindrop falls, but never reaches the earth‘s land surface because it have been intercepted by a tree leaf or a rooftop. Its moisture is returned to the atmosphere by evaporation, transpiration or evapotranspiration. A second raindrop falls and lands in a natural or artificial depression in the earth‘s surface. It is termed depression storage and as such, it never enters into the procces of water removal known as runoff. Another raindrop falls, but it penetrates the land surface, or infiltrates into the ground Chorley, 1978. The amount of infiltration, or infiltration rate, is variable among different soil even for a given soil it is variable and dependent on the previous dampness, or 7 antecendent moisture, condition of the soil. Infiltrated water may become part of the soil‘s field moisture, may continue its percolation through the soil to the water table and become part of the groundwater system, or may respond to gravity and flow down-gradient at shallow soil depths as interflow or throughflow Chorley, 1978. Water travelling as stream channel or throughflow may remain at shallow depth until it discharges into stream channel and becomes channel flow, may enter into groundwater system, or return to the lans surface and is known as return flow. In the latter instance, it becomes that part of surface runoff which is termed overland flow. Other rain drop fall directly into stream channel and other bodies of water and thus contribute to surface runoff. Such water is termed channel precipitation but it not part of overland flow because, in the strict sense, it does not flow over the land surfaceen route to the stream channel. Still other raindrop fall on the land surface. Such flow is termed overland flowand occurs when the number of raindrops, or amount of precipitation, exceeds the infiltration capacity of the soil and depression storagecapacity of the land surface Chorley, 1978. The consumptive utilization of water by evaporation and transpiration must also be included in the total amount of precipitation needed to generate overland flow, but considering the brief time span of overland flow, these effects have much less significance than the infiltration and depression storage capacities. Water enroute downslope as overland flow is term detention storage Chorley, 1978. 8 Precipitation Gross Rainfall P Horton Overland Flow q H Channel Precipitation P c Saturated Overland Flow q s Precipitation Intencity i Return Flow q r Evapotranspiration e t Pipe Flow t Canopy Interception Loss e c Pipe Storage T Interception and Canopy Storage I Unsaturated Throughflow m u Steamflow and Drip s Saturated Throughflow m s Litter Flow L Soil-Moisture Storage M Litter Interception Loss e I Seepage into Bedrock S b Litter Storage L Interflow in Bedrock a Evaporation e Aeration Zone Storage A Depression Storage R P Deep Seepage d Detention Storage R T Baseflow b Infiltration f Groundwater Storage B Figure 2.1 Components of The Hillslope Hidrological Cycle Chorley, 1978

2.5 Hydrological Cycle in the Non-groundwater Basin