Water and Resources Flashcards
Why is water needed to have life?
- Cells are made of water.
- Living organisms are more than 50% made by water.
- Water carries nutrients.
- Water allows biochemical reactions.
- Water can do thermal regulation.
Complete the phrase: “ In a Poisson process, the interarrivals…”
“… are independent and exponentially distributed.” They are continuous random variables.
What do you need to observe a rainfall event?
1) Saturation conditions in the air: water vapor tension must reach the saturation value at the given temperature. Clausius-Clapeyron Equation.
2) Condensation: change of phase, for that, we need a lot of energy that could be given by a catalist.
3) Drops accretion.
What should we know about Cluster Based Models, more specifically Bartlett-Lewis Model?
It has only 5 parameters!
Process of storm generation and process of cell generation are both Poissonian Processes.On the other side, the distribution of the number of cells per event can be proved to be a geometric distribution.
Poissonian processes are used because they are simple, need few parameters and allows an analytical treatment.
What are the Event Based Models?
Are stochastic continuous models for rainfall, based on the separation of the temporal scales that characterize the events.
What is r in the Conservative Downscalling? What are the two intensities?
r it’s a random number uniformly distributed (no preference for any particular value) in the interval from [0,2[.
(jxr1) ; jx(2-r1)
What is the relative saturation?
Amount of water present in a given soil.
What is the Darcy’s Law?
The Darcy’s Law formed the basis of hydrogeology and describes the flow of a fluid through a porous medium.
Define the 2 critical levels of the soil moisture content.
- Sfc: Field capacity. It’s the value of s above which the movement of water is good. Below this value, conductivity is too small.
- Sh: Hygroscopic point. Below this value, water molecules are too strongly attracted to the soil and can not be extracted.
What is the root zone?
The root zone is the uncompacted topsoil layer, with relatively uniform properties, and where we have a competition between evapotranspiration and percolation.
Explain the Horton and Dunne mechanism.
In the Horton mechanism, the rainfall intensity is too high, so the maximum infiltration rate is exceeded. Short storms, very intense.
In the Dunne mechanism, the accumulated rainfall volume is too high so the soil becomes completely saturated. Long storms, low intensity.
Why does the water go up in plants?
The difference between the overall water potential value on the soil (-0.3 MPa) and the value on the atmosphere (-100 MPa) creates a gradient of energy that makes the water go up.
What is sw and s*?
s* is the soil moisture level below which we start to perceive some reductions of ET as comparison to the potential value. Measures the ability of the plant to compensate droughts. Stomata starts closing.
sw is the soil moisture level below which ET is 0, so no water flows up. Stomatas are fully closed.
How are the dynamics of s(t) reflected by the dynamics of the streamflow Q(t)?
Groundwater environments are connecting the rootzone, the soil moisture dynamics and the streamflow dynamics.
What is the Minimum Environmental Flow?
The MEF is a value that indicates the minimum water availablity in streams, below which ecological and biological processes are threated.
