1.. What four types of mathematical models are used in hydrology?
Deterministic, probabilistic, conceptual, and parametric.
2.. What is the Bowen ratio? What does it indicate?
The ratio between sensible (nonevaporative) heat and latent (evaporative) heat (long-wave terrestrial radiation).
It indicates with the time of climate (arid or humid).
3. How are the Dalton, Penman, and Penman-Monteith evaporation equations related?
The Penman combination method included the Dalton (conceptual) method to calculate the mass-transfer evaporation.
The Penman-Monteith method improved the Penman method by calculating the mass-transfer evporation rate based on physical principles.
4. What four factors influence the time of concentration?
- Catchment length (hydraulic length) L
- Channel slope (channel slope) S
- Friction coefficient (Manning) n
- (Effective) rainfall intensity i.
The Kirpich formula has two variables: L and S.
5. What is a rating curve? What factors influence the type and shape of a rating curve? Explain.
A rating curve is a relationship between the discharge (abscissas) and stage (ordinates).
The rating can be unique, calculated with the Manning equation (steady equilibrium).
Nonuniformity and unsteadiness can cause deviations from the equilibrium rating.
Unsteadiness is responsible for a loop in the rating.
The sedimentation effects are short and long-term. The short term effects occur because the boundary friction varies with flow rate.
This explains the shift from low-flow rating to high-flow rating.
The long-term effects relate to aggradation and degradation (unsteady sediment transport).
6. What is a gully?
A gully is a self-formed channel (formed by erosion) which, due to its large size, cannot be obliterated by farming practices.
7. What do the Creager curves depict?
They depict the diffusion that is present in streamflow. The Creager curves state that the greater the catchment area,
the smaller the peak flow per unit of catchment area.
8. To what five factors is to be attributed the recurrence of debris flows in the San Gabriel
Mountains of Northeast Los Angeles?
- The uplift (through tectonism) of the mountain range (reported to be
the highest in the U.S.).
- The type of vegetative ecosystem (mediterranean, chaparral), which has developed adaptations
to survive through droughts, including waxed leaf surfaces to minimize evapotranspiration.
The mediterranean ecosystem
occurs in midlatitudes (30o-35o) that have exposure to
westerlies (trade winds from
the west).
- The wind storms (Santa Ana), which affects the region.
- The wildland fires, propelled by drought and wind,
which recur approximately every thirty years in chaparral ecosystems. The fires vaporize the waxy substances
(in the litter and standing biomass) at the surface,
and condense 1-5 cm inside the soil, creating the hydrophobic soil layer.
- The intense rainfall events, exceeding 1 in/hr,
which follow the fire because of enhanced coalescence in the lower atmosphere due to ash particles
produced by the fire.
Problem 1