PRODUKTIVITAS EKOSISTEM

MATERI & NON-MATERIAL

Regina R.B, Ieke, W.A., dan Soemarno – Des 2012

HASIL AIR

The choices we make today in how we use land and water resources will have enormous

consequences on the future sustainability of earth’s ecosystems and the services they

provide.

Kota yang rawan air tawar akibat menipisnya jumlah air tanah dangkal dan atau terancam

kekeringan , maka hutan lindung harus dibangun di lokasi tangkapan sebagai penyerap, penyimpan,

dan pemasok air.

AgroEkosistem lereng gunung dengan jasa amenitasnya

(foto smno juli 2009)

HASIL AIRVARIABLES AFFECTING WATER YIELD

There is a direct relationship between the amount of water available in a watershed, climate, and climate variability.

The fraction of precipitation that will reach stream channels depends on the amount and type of vegetation cover, the

physiography, and land use(s) of the watershed. Climate is responsible for precipitation quantity, intensity,

and duration, as well as storm distribution within a watershed, the results of which significantly impact

streamflow regimes and the annual hydrograph. As an example, when a relatively large storm occurs in the upper part of a sufficiently large watershed, the resulting

hydrograph will exhibit a lower peak flow, longer time base, and a slower rise to peak.

Higher elevations also undergo potential snow deposition processes (depending on season), which can also affect the

hydrograph by lowering and broadening it.

In watersheds having sufficiently cold temperatures, usually in higher altitudes, snowfall accumulates forming snowpack, and no significant overland or subsurface runoff is displayed

until snowmelt. In the event of an extreme warming event, rapid climate-

induced rain, wind, and subsequent snowmelt (rain on snow, ROS) can result in flashfloods with often costly and

disastrous consequences for communities located in the floodplain.

Diunduh dari: http://www.eoearth.org/article/Variables_affecting_water_yield…………..

22/12/2012

HASIL AIRWHAT IS GROUNDWATER?

Rainwater percolates into the earth. Soil and rock are like a giant sponge, full of holes - typically tiny pores and cracks just millimetres in size. Below the water table, these holes are full of water. This is groundwater. Groundwater slowly

travels through connected pores and cracks just centimetres to metres per year.

Diunduh dari: http://www.nrcan.gc.ca/earth-sciences/products-services/mapping-product/

geoscape/waterscape/bowen-island/6041………….. 22/12/2012

HASIL AIRWater table ups and downs through the

seasons

The amount of water stored underground changes through the seasons. As winter and spring rains infiltrate the ground, stored

groundwater increases and the water table rises.

When the rains stop, the water table falls as groundwater leaks into streams and the ocean. Well pumping also removes water and

lowers the water table. Excessive pumping of groundwater can result in long-term depletion of groundwater storage.

Diunduh dari: http://www.nrcan.gc.ca/earth-sciences/products-services/mapping-product/

geoscape/waterscape/bowen-island/6041………….. 22/12/2012

HASIL AIRUnderground lakes and rivers?

Not on Bowen Island. Large underground streams and lakes only occur in limestone cave systems. Limestone is unique

as it dissolves in water, allowing caves to form. Bowen Island's granitic and volcanic rocks do not dissolve in water

and so lack cave systems.

Diunduh dari: http://www.nrcan.gc.ca/earth-sciences/products-services/mapping-product/

geoscape/waterscape/bowen-island/6041………….. 22/12/2012

HASIL AIRTapping into water stored underground

Any body of rock or sediment that yields useful amounts of water is an aquifer. Bowen Island has two types of aquifer: fractured rock,

and sand and gravel layers. The amount of water stored in fractured rock is typically limited, and these aquifers can run low during the summer drought. Sand and gravel can store more water and these aquifers are less likely to dry up in the summer. Shallow- dug wells

can dry up as the water table falls during the summer.

Diunduh dari: http://www.nrcan.gc.ca/earth-sciences/products-services/mapping-product/

geoscape/waterscape/bowen-island/6041………….. 22/12/2012

Groundwater flows from upland recharge areas to valley discharge areas

HASIL AIRSurface water and ground water relations.

All groundwater pumping comes from capture; the greater the intensity of pumping, the greater the capture. Capture comes from decreases in natural discharge and increases in recharge. Natural

discharge supports riparian, wetland, and other groundwater-dependent ecosystems, as well as the baseflow of streams and rivers. Capture depends on usage, and it is not related to size or hydrogeological characteristics of the aquifer, or to the natural

recharge. Sustainable yield depends on the amount of capture, and

whether this amount can be accepted as a reasonable compromise between a policy of little or no use, on one

extreme, and the sequestration of all natural discharge, on the other extreme.

Diunduh dari: http://ponce.sdsu.edu/groundwater_sustainable_yield.html………….. 22/12/2012

HASIL AIR. Recharge and discharge in groundwater systems:

(a) pristine, (b) developed, (c) depleted.

In the pristine groundwater system (Fig. 4 a), [average] natural recharge is equal to [average] natural discharge, net recharge is zero, and pumping is

zero. Thus, natural recharge (the blue block on the left) equals natural discharge (the blue block on the right) (Fig. 4 a).

In the developed groundwater system (Fig. 4 b), captured recharge (the brown block on the left) is the increase in recharge induced by pumping. Likewise,

captured discharge (the brown block on the right) is the decrease in discharge induced by pumping. Then, residual discharge (the blue block on the right) is

equal to natural recharge (the blue block on the left) minus captured discharge. Net recharge is equal to the sum of captured recharge plus

captured discharge. Net recharge varies with the intensity of pumping; the greater the intensity of pumping, the greater the net recharge. Pumping in the developed groundwater system is equal to net recharge, i.e., capture (Fig. 4 b).

In addition to captured recharge and captured discharge, the depleted groundwater system (Fig. 4 c) also features captured storage (the dark brown block on the left). Net recharge is equal to captured recharge plus captured

discharge. Pumping in the depleted groundwater system is equal to net recharge plus captured storage (Fig. 4 c).

Diunduh dari: http://ponce.sdsu.edu/groundwater_sustainable_yield.html…………..

22/12/2012

HASIL AIRAll ground water of economic importance is in constant

movement through a porous rock stratum, from a place of recharge to a place of discharge.

Available recharge is the sum of unrejected and rejected recharge . The unrejected recharge is the natural recharge; the rejected

recharge is the portion of available recharge rejected by [portions of] an aquifer on account of being full (at least part of the time). To

assure maximum utilization of the supply, Theis argued that groundwater development should tap primarily the rejected recharge

and, secondarily, the evapotranspiration by non-productive vegetation. Thus, he defined perennial safe yield as equal to the

amount of rejected recharge plus the fraction of natural discharge that it is feasible to utilize.

According to Theis (1940), where rejected recharge is zero, the only way to replace the well discharge is by artificial recharge. The latter

is the increase in recharge induced by human design.

Diunduh dari: http://ponce.sdsu.edu/groundwater_sustainable_yield.html………….. 22/12/2012

HASIL AIRThe age of the forest determines the amount of water runoff.

The Soil/Water Hydrology Process (Source: Predicting Water Yields From Mountain Ash Forest Catchments’ Industry Report of the Co-operative Research Centre for Catchment Hydrology, April 1998.

Fig 1, Pg 1.)

Diunduh dari: http://www.oren.org.au/issues/water/report/8crcchtrees.htm…………..

22/12/2012

HASIL AIR. WATER YIELD MODEL

The water yield model is based on the Budyko curve and annual average precipitation. First, we determine annual water yield (Yjx) for

each pixel on the landscape (indexed by x = 1,2,...,X) as follows:

where, AETxj is the annual actual evapotranspiration on pixel x with LULC j and P:sub:`x`* is the annual precipitation on pixel *x.

Diunduh dari: http://ncp-dev.stanford.edu/~dataportal/invest-releases/documentation/current_release/reservoirhydropowerproduction.html………….. 22/12/2012

Conceptual diagram of the water balance model used in the hydropower production model. The water cycle is simplified, including only the parameters

shown in color, and ignoring the parameters shown in gray. Yield, as calculated by this step of the model, is then adjusted for other consumptive uses and applied to

hydropower energy and value estimates.

HASIL AIRThe evapotranspiration partition of the water balance, , is an

approximation of the Budyko curve developed by Zhang et al. (2001):

where, is the dimensionless Budyko Dryness index on pixel x with LULC j, defined as the ratio of potential evapotranspiration to precipitation (Budyko 1974) and is a modified dimensionless ratio of plant accessible water storage to expected precipitation during the year. As defined by Zhang et al. (2001) is a non-physical parameter to characterize the natural climatic-soil

properties.

where is the volumetric (mm) plant available water content. The soil texture and effective soil depth define , which establishes the amount of water that

can be held and released in the soil for use by a plant, estimated as the product of the difference between field capacity and wilting point and the

minimum of soil depth and root depth. Z is a seasonality factor that presents the seasonal rainfall distribution and rainfall depths. In areas of winter rains,

we expect to have Z on the order of 10, in humid areas with rain events distributed throughout the year or regions with summer rains the Z is on the order of 1. While we calculate , in some cases specific biome values already exist based on water availability and soil-water storage (Milly 1994, Potter et

al. 2005, Donohue et al. 2007).Finally, we define the Budyko dryness index, where values that are greater than one denote pixels that are potentially arid (Budyko 1974), as follows:

where, ETox is the reference evapotranspiration from pixel x and is the plant (vegetation) evapotranspiration coefficient associated with the LULC j on pixel x. ETox represents an index of climatic demand while is largely determined

by x‘s vegetative characteristics (Allen et al. 1998).

The water yield model script generates and outputs the total and average water yield at the sub-basin level.

Diunduh dari: http://ncp-dev.stanford.edu/~dataportal/invest-releases/documentation/current_release/reservoirhydropowerproduction.html………….. 22/12/2012

HASIL AIR

Evaluating ecosystem services in production versus water yield and water quality in mountainous

landscapes.

Diunduh dari: https://www.bayceer.uni-bayreuth.de/terreco/………….. 22/12/2012

HASIL AIRManaging Arid and Semi-Arid Watersheds

Matter is Not Created or Destroyed—The physical law of continuity stated simply is that "matter is neither created or destroyed". A given environment or ecosystem over a period of time receives an average input of precipitation and produces an average output of streamflow. The difference between these two amounts is basically what is used

by the vegetation growing on the site. Because matter or in this example precipitation is neither created or destroyed, if one can change the amount of water used by the vegetation there will be more water available for streamflow or percolation into the soil.

The key to increasing water yield is the replacement of deep-rooted or high water using plants with shallow-rooted or low

water using plants.

Differences in water use by shallow and deep rooted plants

Diunduh dari: http://www.rmrs.nau.edu/watersheds/highlands/research.php………….. 22/12/2012

HASIL AIRWATER YIELD OPPORTUNITIES

Water yield improvement, as it pertains to forest and rangelands, is based on the premise that streamflow and/or ground water are

increased by an amount equal to the net reduction in evapotranspiration (Hibbert 1979).

According to Hibbert, little opportunity exists to reduce transpiration where precipitation is less than about 460 mm(18 inches) (Figure

from Hibbert) and is exceeded by potential evapotranspiration (warm, dry portions in figure ), because precipitation does not

penetrate far into the soil, and one cover type is about as efficient as another in using the available water.

The greatest opportunity to increase runoff by reducing transpiration exists where precipitation exceeds 460 mm (18 inches) and potential

evapotranspiration (determined by the Thornthwaite method) exceeds 380 mm (15 inches). This kind of climate promotes vigorous

growth of vegetation capable of using large amounts of water. Therefore, modifying plant cover under these conditions can

substantially increase water yield.

Vegetation and Rainwater Management

Vegetation can be managed ways to reduce evapotranspiration:

1. Decrease stand density by various practices to reduce transpiration and interception.

2. Convert plant cover from one cover type to another that uses less water (type conversion).

3. Create openings in forest cover to reduce transpiration and to redistribute snow, thus concentrating the rainwater to reduce evaporation, to increase snowmelt efficiency, and to enhance contributions to streamflow.

4. Establish trees, large shrubs, or fences in windswept, treeless areas to pile snow in large drifts, thereby reducing evaporation losses from the rainwater.

Diunduh dari: http://www.rmrs.nau.edu/watersheds/highlands/research.php………….. 22/12/2012

19

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