CLIMATE CHANGES

INTRODUCTION

In the proposed model some aspects of the consequences of climate changes colud be monitored considering whose characterisitics elements of hydrological events so as they where defined in the previous paragraphs.

Infact, trought the monitoring of changes of these elements it is also possible to define the changes in the hydrological response of a generic piece of territory and above all it si possible to define also how changes the concepts of risk and danger (so as they are intended) during time.

These elements are peculiars and reflect both at the same time weather events characteristics and geomorphological aspects of the investigated territory.

In particular they reflect at first the characteristics of local meteoric inflow regime and then local geomorphology's aspects.

1_CLIMATE CHANGE AND LOCAL HYDROLOGICAL RESPONSE

The characteristic elements of a hydrological event represented within a graphical summary solution are called CHARACTERISTIC because they highlight its peculiarities.

These characteristic elements are, above all, the ALPHA angles, which the DRY and WETTED limits form with the X-axis, and the BETA angle, which the aforementioned limits form with each other.

These factors are a function of both the temporal trend of the inflowing water volumes, evaluated within the reference territorial units, and the surface area of those units.

In general, they are a function of local weather/climate and geomorphological characteristics, and their values vary with the factors describing these characteristics.

The weather/climate factor varies both in space and time, and the geomorphological factor is the same.

The first depends on local climate characteristics, which vary with latitude and altitude, as well as other factors that make them change over time.

Local geomorphological characteristics also change over space and time and are a function of exogenous and endogenous modeling agents.

Climate change, which is always ongoing, is the main cause of variations in local climate characteristics over time, such as average monthly precipitation.

This parameter or distinctive element of the climate conditions of a given area of the globe in turn affects the monthly hydrological regime as defined and described above. Therefore, in general, it can be said that climate change could also produce a slow or sudden change in the local hydrological regime, which in the graphical summary solution is defined between the two limits DRY and WETTED as well as by the angle formed between them, called BETA.

2_HYDROLOGICAL AND HYDROGEOLOGICAL STABILITY

The importance of these principles or concepts, particularly those regarding characteristic elements, is evident considering that in the LOCAL HYDROLOGICAL RESPONSE model we hypothesize the existence of an additional field called the HYDROLOGICAL and HYDROGEOLOGICAL STABILITY FIELD.

This particular field is understood to consist of pairs of AREA_VOLUME values for which no WATER CRISIS conditions exist within the investigated territorial area and for which, at the same time, no meteorological events capable of generating impulses that cause hydrological instability phenomena.

This stability field will be defined within two limits, an upper and a lower one, of which the first marks the transition to adverse and critical weather/climate conditions that generate instability phenomena, while the lower marks the transition to weather/climate conditions that generate water crisis conditions for the entire environmental context.

These two limits will intersect at the origin of the graphical synthesis solution, also forming an angle called GAMMA, which is smaller than BETA.

Therefore, the STABILITY FIELD for a given geographical area of the globe, defined in this way, is assumed to be included within the FIELD of the CONSOLIDATED HYDROLOGICAL REGIME.

Considerations on the variability of characteristic elements in space and time can also be made for the same elements that define the STABILITY FIELD.

That is, as the geographical position varies, the stability field can be more or less extensive, and the same occurs when considering the meteorological and climatic evolution of a given area over time, as in the case of climate change.

3_EFFECTS OF CLIMATE CHANGES ON CHARACTERISTICS ELEMENTS

A firsrt important effect of the climate changes on the local hydrological repsonse so as is described in the porposed model is the rotation of the tendency lines assumed as dry and wetted limits.

Infact during the process of climate changes local the inflows regime changes and these limits rotate all around the origin of the AXIS with some differences.

At the same time in cause of that ALFA and BETA angles values change also. 

These changes of values are not neccessary equals and above all they are not always positive.

Infact rotations of angles colud verify or versus left or versus right and theyr values colud be or positive or negative.

That means that some times BETA or ALFA values could increase and some times decrease.

It's important to unedrstand that the hypothesis is that the dry and the wetted limits rotations are not yncronized. 

4_EFFECTS OF CLIMATE CHANGES ON LOCAL HYDROLOGICAL RESPONSE

Migrations trought rotation of the dry and the wetted limit around the origin of AXIS means that at the same time the values of ALFA and BETA angles change and with them changes also the value of the GAMMA angle (HYDROLOGICAL and HYDROGEOLOGICAL STABILITY).

If these characterisitics elements change so will change also the hydrological response of a generic piece of territory and if we consider the seasonal cycle as a climatological event some considerations could be done.

These migrations could be not only sinchronized (dry limit and wetted limit migrate versus the same direction) but also irregulars with the migrations oriented to opposite directions.

Inthese cases, in general if the wetted limit migrates to hight values of inflow water's volumes while the driest limit migrates to low values the local territory will be characterizzed by an inflow waters regime very differentiated while in the opposite case regime will be homogeneus.

If the BETA's value decrease the water's volumes inflow regime will be more homogenous and the local territory will be subjected to a small range of values of inflow waters since driest period until wettest season.

If BETA's values increase the water's volumes inflow regime will be more eterogenous and the local territory will be subjected to a wide range of values of inflow waters since driest period until wettest season.

In generalr it exist a set of various possibilities whose are not yet analyzed and that need to be interpretated.

4.1_THE CASE OF THE "TIBER RIVER"

(MIGRATION_ROTATION OF LIMITS WITH CONSTANT MORPHOLOGY)

Below is a partial example of the migration or rotation process of the DRY and WETTED limits for the TIBER RIVER, a basin considered to be large.

The basin has been divided into 250 meters elevation bands, except for the last one.

The event geometries for the DRY limit are shown for the period 1960-1990 and the WETTED limit for the same time interval.

The event geometries for the DRY and WETTED limits for the period 1970-2000 are also shown.

The example is said to be partial because the time intervals considered and processed partially overlap. Furthermore, the example can be considered risky, as the basin is of considerable size and the internal climate is highly variable and complex.

Finally, in this example, the morphology is assumed to have remained unchanged over the 40-year period considered and/or not to have changed excessively.

In general we could say that hypsographic curve representing basin’s morphology has not cahnged significatively during this period of time.

This aspect is highlighted by the constant trend in the surface area values of the reference territorial units considered.

FIG_1: PERIOD 1960_1990

FIG_2: PERIOD 1970_2000

FIG_3: COMPARING RESULTS MIGRATIONS_ROTATION APPEARS AND THE MAIN CONDITION IS THAT MORPHOLOGY REMAINS COSTANT.