Hydrological Processes and Water Management

1. What is the hydrological cycle and how can water balance be quantified?

The hydrological cycle is the water’s cycle caused by solar energy. It can be quantified by the following equation: P = Q + AE +-AW (precipitation= runoff + actual evapotraspiration +-Changes in water storage (surface, soil water, ground water)). In this cycle, we have to consider also the change of state of water aggregation, from ice to liquid and vapour, and also snow, hoarfrost, etc.

2. What are both catchment and management characteristics that significantly affect surface runoff?

The catchment is the surface water flows through one outlet and it’s determined by waterdivide. It has two kinds of characteristics: the firsts are physio-geographical (climate, geology, soil properties like hydraulic conductivity, sorptivity, quantity of loam, sand and clay and their properties). The second type is physio- geometrical (area [km2], slope [%], river length [m, km], bottom slope [%], density of river network [-], percentage of forestation [%]).

For the management, we have these following features: land use (urban, forest), road system, storages, biometrical measures, technical measures (both to erosion control).

3. What are the major reasons for floods?

Depth of rainfall and its intensity, antecedent saturation (how much water was contained before the flood), existing or historical flood control measures to mitigate floods. 

4. How to mitigate harmful flood impacts?

One way to mitigate flood impacts is transforming surface runoff through infiltration to soil water and to groundwater. But is possible also using reserve storages like cascade of reservoirs, polders, diking, etc. Or other biotechnical measures such as terraces, dikes, dams, ditches, bifurcations and confluences, hydraulic constructions in rivers (weirs, chutes, slips, bottom drops, drop spillway, etc.)

5. What is the difference between a dam and a dike on a river?

Dam: is perpendicular to the river bank, and dike is parallel with the river bank (longitudinal shape). DISEGNI!!

6. Define rainfall depth and intensity?

Depth (R) is rain or rainfall in mm, and intensity (I) is the depth divided by time in mm/min or mm/hr (I=R/t). 

7. What are the basic principles for climate change scenarios?

The basic principles are based on the perpendicular axes system: the vertical axe is global/regional and the horizontal is control production/free production.

8. What are the major flood control and water erosion measures?

For flood control, the measures can be the following: land use, storage, weirs, dikes, polders, mobile gates in urbanized areas, etc. For water erosion control, we can intervene in the land use (grassing, afforestation), built ditches, terraces, infiltration belts, etc. 

9. Can you express the relation between hydrological probability and return period?

The probability (p) in a statistical sense is a decimal fraction and the return period (N) is an estimate of the probability of an event, such as a flood or a river discharge flow to occur. P= 1/N

10. Why is water scarcity becoming a more actual global problem? Give the major reasons.

The water scarcity is due to intensive agriculture and bad management (unbalance between plant growing and animal husbandry), possible climate change and water quality. But for the climate change, in accordance with the Paris Conference (12/12/2015), all countries’ governments agreed that the temperatures don’t increase more than 2°C in the year 2100. 

11. What forces do affect the shape of rivers in a landscape (river meandering)?

Forces: uneven impact of non-regular friction along wetted perimeter; local centrifugal forces (cross-sectional); global centrifugal forces (Coriolis). 

12. How to reduce surface runoff (or overland flow) on a catchment? 

By biotechnical measures installation: to increase infiltration and water storage by reducing the velocity of water, infiltration ditches, or by other measures like terraces, infiltration belts, etc.). In principles by biotechnical measures, that means building obstacles and barriers to decelerate water velocity and impact water infiltration by these measures. 

13. How to increase river capacity?

By to double cross-section profile (double trapezoidal profile) or lower (kinet) channel with berms and floodplains in open landscape and limiting walls in urbanized areas.

14. What are the major outlines for river restoration (revitalization)?

Water quality: self-purification of water (central waste water treatment) and oxygenation, that means changing chutes and pools.
Biological regime: migration of biota and riparian vegetation. Free mobility for biota (fauna).
Diversification: in the situation: meandering; in a longitudinal profile: changing chutes and pools or to avoid obstacles; in cross-section profile: changing discharge capacity. It also increases the bio-diversification for restoration.

Movable bottom: various morphology helps invertebrates amphibious, fish, etc. It enables also migrate upstream and downstream.
Riparian vegetation: increase a botanical richness of species and amount of refuges. 

20. The channel cross-section area S = 5 m2 and water velocity flowing through v = 0.5 m/s. What is the discharge Q?

From the continuity eq: Q = v*S = 0.5*5=2.5 m3/s

21. Use one sentence for Water Resources Management definition?

Keeping a good balance between water demand and water resources. The second sentence might be that water resources have to be protected. 

23. What is the role of an infiltration ditch in a landscape?

To keep water excess and to transfer it for a storage water or groundwater mitigating the negative impact of runoff. So, is important that the slope of the diches is going to 0. Cross section profiles: 

24. Describe very briefly the main problems in the delta of the Nile River after building the Aswan high dam?

This dam was built because of energy supply and stopes the natural fluctuating water level in Nile River. Irrigation by floods and drainage by water recession was interrupted and water logging was going out. To keep the harvest 2 to