Starikov
N.P.
COMPLEX IRRIGATION-ENERGETIC
USE OF WATER RESOURCES, FLOW REGULATION AND WATER ALLOCATION ON INTER-STATE
LEVEL AT AN ARID ZONE.
Investigations conducted
by the author related to the rational water resources use's theory
and optimal work regime control of reservoirs of long regulation cycle
applicable to an arid zone, and analysis of actual use of operating
reservoirs of Syrdarya and Amudarya water-economy systems for the
last 25 years allow make a number of generalizations and conclusions
on further development and deepening of the developed subject, those
are formulated in following theses given below.
1. "Working out
of strategy and complex of work regime optimization programs of complex
cascade of reservoirs in an arid zone making an allowance for hydro-energetic
requirements" in its nature is a scientifically-practical problem
in the subject being studied, oriented for achievement of main goals
of Automated Operation System of river basin (ASUB-RIVER) - gaining
maximum productive efficiency from the whole multipurpose water-resources
scheme (MWRS) of the basin. Research aspect of this problem task is
aimed to development of rules on ensuring rational and sustainable
(for many years) water return regime of the basin water-economy system
(WES) under availability of some uncertainties in an initial information.
Principal point of the subject studies is optimization of work regime
control of the cascade of reservoirs of complex irrigation-energetic
purpose as main functional elements of the WES, those are intended
put in order everyday flow regime of rivers (forming-production subsystem)
according with requirements of WEC's branches (WES's consuming subsystem).
In current conditions of maintenance of operating reservoirs (under
their fixed parameters and concretized location along a stem stream
in combination with irrigation development the river run-off, which
are close to the limit one) problem of the most full and, respectively,
rational water resources (WR) use is principal. It mainly comes (is
brought) to definition such a work regime both for individual reservoir
and for a cascade of ones as a whole (i.e. sequence and rate of their
discharge and filling up), that, upon the best meeting water consumers'
requirements, would: firstly, promote to decrease of "idle"
(for power engineering) and "non-scheduled" (for irrigation)
discharges, water loss reduction due to evaporation from the reservoir's
surface, and keeping water mineralization in prescribed limits in
the stem stream; secondly, promote to maximization of energetic efficiency
of hydro-power stations located in the basin (not only that included
in hydraulic works of the reservoirs themselves).
The second issue relevant to a great extent to aspect of "WR
use (consumption) rationalization", which is solved within the
framework of a consuming subsystem, is inter-branch water allocation
and redistribution. As for the basins of Syrdarya and Amudarya rivers,
this mainly concerns irrigation and energy, and this problem physically
solved again through the reservoirs' work regime, by sharing between
them regulation functions in the cascade.
2. Solution of above-said
problems connected with accounting great number system factors, some
of those we should note:
a) flow controlled
by the reservoirs, relative (to the flow rate) capacity of the reservoirs,
their commanding position over irrigated tracts of land;
b) probabilistic nature of the flow, availability non-anisochronousness
and non-sinchronism of regime between separate water currents of
the basin, low authenticity of the flow forecasts;
c) variability requirements (by territory and time) of WEC's branches
to amount and regime of water takings, connected with their increase
or inter-industry rationalization, and, in this connection, change
of amount and time of coming return flow, what influences, on the
whole, upon capacity and flow regime actually regulated in the basin;
d) energy-potentiality of water supply and transit flow (taking
into account pressure of both its and down-located hydropower stations)
of each complex hydro-system, shortage of fuel and energetic balance
of a district of the basin being considered; fuel cost (trailing
expenditures), possibility of its storage (that is cost of its seasonal
storing) and so forth.
In addition to factors mentioned, it is necessary to note that physically
capacity of operating reservoirs changes in time (it is decreased
owing to silting and marginal erosion), and introduction of new
reservoirs during service of the ASUB (introduction of the Kambarata
reservoir on the Naryn river, upper the Toctogul hydrosystem, in
the Syrdarya's basin, and the Rogun reservoir on the Vakhsh river,
upper the Nurek one, in the Amudarya's basin is planned), what brings
to re-sharing of regime functions between all the operating reservoirs.
Most of enumerated factors is associated to uncertainty, and sometimes
to inadequate source information, and this predestines capacity
and complexity of solution of set of problems on cascade of reservoirs'
work regime optimization, and respectively its economic-mathematical
model (EMM).
3. Tension of water-economy
situation in Central Asia, especially in the Syrdarya WES, greatly
influences upon use regime of the operating reservoirs' capacity,
and, as service practice for the last 25 years is evident of, it leads
to many violations of the design order of their work and to divergens
from the service (design) parameters. Firstly the divergens caused
by inter-branch contradictions of requirements on water-delivery regime
between departments of water-economy and energy, after disintegration
of the Soviet Union, thanks to landscape specifics of the Surdarya's
basin they became interstate. In particular, order of fillings and
limits of limiting drawdown amount of the reservoirs' dischargeable
capacities of, at the first place, the Toctogul one, supposed to make
compensating many-year flow regulation of Syrdarya according to irrigation
requirements. Higher winter drawdowns from the Toctogul reservoir
for energetic purpose, being in common practice for the last 12 years
(by Kirghyzstan), broke not only the design regulations, but the very
principles of many-year flow regulation: drawdown of many-year capacity
supply realized in high water capacity years (natural inflow for that
period was higher than the outflow rate), what is fraught with considerable
damage from water deficit in agriculture (for Uzbekistan and Kazakhstan),
as well as in power engineering (for Kirghizstan) when water shortage
period comes. Previous years partial drawdown of reservoirs' dead
zone for irrigation purpose was in common practice, what caused sizeable
damage to the region's power engineering (essentially throughout the
cascade of Nijnearynskiy hydroelectric power station).
4. Observed in the Syrdarya WES water use excess over guaranteed water
delivery, stipulated in the design, makes hard filling the reservoirs,
and brings the system to situation of "unstable regulation regime",
when water deficit becomes more frequent and deeper. To eliminate
this, introduction of limit for water use is required in a practical
maintenance of WES, and it is necessary to include into the part of
EMM development on optimal management of the reservoirs maintenance
regimes an elaboration task of ensured water delivery by the cascade
of reservoirs, reflecting therein both technical parameters of the
WES's objects and water-economical situation forming (at that moment)
in the basin.
5. Target specifics
of the flow regulation optimization process for a river of an arid
zone at the stage of its WR development consists in that so as total
delivery of the whole WES by non-return water use in years normal
by water-balance situation (non-deficit one under discharged and non-excess
one under filled up to the normal maximum operating level reservoirs)
has to be consistent with the value of secure requirements (without
short delivery and without exceeding). By observing this term the
fullest and, correspondingly rational, use of WR is ensured.
6. The most severe difficulties
in work optimization of complex cascade during exploitation period
represent ensuring rational regime of drawdown-filling of reservoirs
on the inflows (directly regulating only part of the flow of the main
river's basin), and ones used in many-year compensation regime. Among
such objects in the Syrdarya WES at present is the operated Toctogul
hydrosystem, water yield in the reservoir site of that amounts to
30 % of the main river's flow, i.e. of the Syrdarya river (11.5 of
37.5 km3/year). In prospect Pskemskiy (the Chirchik river's basin)
and Rogunskiy (on the Vakhsh r.) hydrosystems can be used in the same
regime. Concrete drawdown rate from a compensating reservoir in each
year should be determined based upon developing current water balance
of the whole WES (over the end station of the basin's main river)
observing the term of maintaining adjusted water delivery regime stated
above.
7. In the design aspect,
on the base of retrospective (hence, determinate) information, solution
of this problem, although it is laborious, is not difficult. From
day-to-day-exploitation consideration its realization is too hard
because it requires for an immediate information (for the present
situation) about inflows and drawdowns at the tail-water over all
reservoirs of the cascade, about all water discharge and off-taking
in the basin, and channel inflow and estimation of return water (RW).
Lack of proper quantity facilities controlling WR in WES allows solving
the mentioned problem only highly approximately, using for this purpose
design statistics (calculations over retrospective years of time)
on regulation parameters for a main reservoir-compensator, such as
stabilizing range of annual drawdowns, limitation (non-exceeding)
by maximum design values of one-year drawdowns of long-standing supply
of regulating capacity and so on. According to the design data on
scheme of complex use of water resource protecting (KIOVR) of the
Syrdarya r., for the Toctogul reservoir, where the dischargeable capacity
is 14 km3, such a one year-drawdown (within the framework of used
in practice ensured for 90 % water delivery) has not to exceed around
6 km3.
8. In order to reduce
wasteful loss of the flow for evaporation from the water surface,
as well as reduce "non-scheduled" water discharge under
filled reservoirs capacity, one can recommend:
application of "altitude" (regarding to subcommand irrigation
tracts of land) principle in technologic succession of cycle "discharge-filling"
of reservoirs of a cascade (firstly capacities of downstream ones
are discharged, and then - of upstream ones; filling is carried out
in inverted sequence);
avoiding within-year redoubling (filling some while synchronously
discharging others) when using cascade's reservoirs capacities. An
exception is acceptable in special case and under an appropriate feasibility
study on the base of a comparison of inter-branch efficiencies and
damages (see below the item 10).
Application of the mentioned principles touches upon a subject of
seasonal productiveness in the MWRS's branches, and requires for,
on the one hand, including into the EMM's structure tasks on productiveness
estimation of the flow being lost, and, on the other hand, definition
of difference in productiveness between the branches, with following
definition of the total maximum productiveness in the WES for a year
on the whole. General complex of programs on management by long-term
maintenance regime of a cascade of reservoirs, including as a component
part in the system of information-calculating complex of control of
WES. Automated control systems of a basin has to be oriented to achievement
of one of the main goal - gaining maximum productive efficiency from
the whole multipurpose water-resources scheme of the WES when ensuring
stable long-term regime of its functioning.
9. Complex's structure
(composition of tasks solved by them) needs to reflect specifics of
natural, economical and technological conditions inherent to water-economical
systems of an arid zone, namely:
general deficiency of WR (potential excess of possible to irrigation
lands over irrigation ability of the rivers);
prevailing irrigated lands among water consumers of MWRS (by a water-taking
amount), and among water users - hydro-power engineering, what brings
to forming a specific economical above-system - irrigation - energetic
WES (IEWES);
instability of irrigation requirements (mostly increase) on the amounts
and in the regime during the development process of WES, leading to
change of the capacity required in the reservoirs for flow regulation;
time variation (decrease in the result of bed processes) of dischargeable
capacity of the reservoirs, availability and, at the same time, continuous
changes of RW arrival, constant change of capacity and regime of the
very regulable domestic flow itself over the stem stream, bringing
to the necessity, in the course of WES functioning, of making regular
inspection of maximum capability of its water delivery allowing for
the current technical state of the system's objects.
10. Continuous increase
of water use for irrigation leads to inter-branch (primarily between
power engineering and irrigation) water resource allocation, which
can be carried out applying EMM of water efficiency comparison in
these branches. On the base of the mentioned EMM practical calculations
on efficiency comparison of "purely" irrigation and "purely"
energetic variants of the Toctogul reservoir's regime have been performed,
those gave the following results (they were defined in 1984's prices):
the agriculture efficiency by the irrigation variant, ensured by the
flow regulation in the Toctogul hydro-system (THS), and in which about
94 % of calculated costs of other rural enterprises is used, by total
gross production - 1530-1700 mln. roubles, by total net income (TNI)
- 900-1000 mln. roubles; and damage to the power engineering, connected
with winter output reduction by the Toctogul hydro-power station (HPS)
and corresponding overspending of more expensive winter fuel in the
power engineering, was 17 - 19 mln. roubles/year. Basing on given
factors, one can conclude that the THS because of keeping irrigation
regime (by share in general man/hour) has the right to pretend to
take its part out of TNI to 45-50 mln. roubles/year (not less than
the value of damage to the power engineering said above).
A principal scheme underlying the EMM of comparison said of is shown
below.
Principal efficiency
comparison scheme of flow redistribution between the agriculture (irrigation)
and power engineering (regime of hydro-power station)
On the scheme:
a) annual (average monthly costs - Q) water-economical balance of
WES;
b) relationship of ensured (winter) power to energetic discharge
Nens = f( );
c) the same, of annual capacity of irrigation water delivery Wir
= f(Qens);
d) dependency of HPS' share in the power system's daily schedule
N"HPS = f(Nens);
e) scheme of change of HPS' share in the power system's daily schedule
when changing water-economical balance (WEB).
Conditional indications:
I and II - variants of WEB in the WES;
HHPSi - average pressure of HPS in a i-th month;
Qenmin and Qenmax - limits for water discharge under "purely"
energetic regime;
Other PS - other "peak" power stations (conditionally
HPS) of the power system.
11. Considerable influence
on regulation regime and change of ensured water delivery to the branches
in some cases can be made by water supply as well. Owing to reconstruction
of hydro-reclamation systems, reorientation of the regions in crop
cultivation, some changes in inter-branch efficiency of irrigation
water, and, therefore, in territorial water allocation, take place.
Market changes of prices or trailing evaluations of branch output
(including fuel) can play not a little part in these processes. All
this brings to a need for including in the complex special groups
of tasks, which can be named as "expert-evaluating," namely:
more accurate definition of economical indices of criteria of water
resources use (trailing evaluations of power energy, crop production,
specific irrigation and hydro-energetic efficiency of water);
more accurate definition of inter-branch limits (in particular, low
limit of minimum water discharge for power engineering);
more accurate definition (when allocation) of territorial limits of
water delivery (economically-residential and ecological);
more accurate definition (in comparison to the design data) of total
gross and net water delivery by the cascade of reservoirs of the WES
(values of ensured water delivery).
Taking into account all the above-stated the WES' features of an arid
zone, a general optimization complex can be presented by the following
set of tasks (without detailing their individual groups) (see the
table below):
|
Structure
of technical-economic optimization problems of a cascade of reservoirs'
long-term work regime in an irrigation-energetic WES
|
| Index
and name of problems and subproblems |
Where
the input information arrives from |
Where
the output information is delivered to |
| 1.
Calculations of trailing branch evaluations |
| 1.1
Calculation of trailing evaluations of agricultural efficiency of
irrigation water1.1. |
External information in the input flow (EIIF) and Reference Data
(constant properties of constructions) (RD) |
To 2.3, 3.2, 3.3.7, 3.3.8 and 3.3.9 |
| 1.2
Calculation of trailing evaluations of power energy (CEPE) |
|
|
|
1.2.0 Auxiliary program inputting design water-energetic indices
of HPS |
EIIF |
To 1.2.1, 1.2.2, 1.3, 2.2 and 2.3 |
|
1.2.1 Calculation of annual power-energy balance (PEB) of the power
system (PS) |
From 1.2.0 and EIIF |
To 1.2., 1.2.3, 1.3, 3.3.5 and 3.3.6 |
|
1.2.2 Calculation of annual maximum powers balance (MPB) of the
PS. |
From 1.2.0, 1.2.1 and EIIF |
To 1.2.3 and 3.3.5 |
|
1.2.3 Definition of CEPE by variants of WEB |
From 1.2.0, 1.2.1 and RD (on fuel values) |
To 1.3, 2.2 and 2.3 |
| 1.3
Calculation of specific energetic efficiency of water (on the cascade's
HPS) |
From 1.2.0, 1.2.1 and 1.2.3 |
To 2.2 and 2.3 |
| 2.
Correction-optimization calculations |
| 2.1
Calculation of ensured water delivery by the cascade of reservoirs |
From EIIF and RD (on water resources) |
To 2.2 and 3.1 |
| 2.2
Calculation of economical maximum limit of hydro-energy interests |
From 1.2.0 and 1.3 |
To 3.1 and 3.2 |
| 2.3
Calculation of limit for water resources use to irrigation in the
WES (accounting for other water consumers) |
From 1.1, 1.2.0, 1.3 and EIIF |
To 3.1 and 3.2 |
| 3.
Calculations of planned regime of the reservoirs |
| 3.1
Calculation of annual water delivery of the WES (taking into account
filling up of the reservoirs and flow forecast) |
From 2.1, 2.2, 2.3 and EIIF |
To 3.2 and 3.3.1 |
| 3.2
Calculation of rational territorial water allocation (on river stations
and reservoirs) |
From 1.1, 2.2, 2.3, 3.1 and RD (water-economic characteristics of
reservoirs) |
To 3.3.1, 3.3.2, 3.3.7 and 3.3.9 |
| 3.3
Calculation of rational annual regime of flow regulation by reservoirs
|
|
|
3.3.1 Forming variants of WEB (requirements to reservoirs' work
regime) |
From 3.1, 3.2 and EIIF |
To 3.3.2, 3.3.6, 3.3.7, 3.3.9 and 3.3.10 |
|
3.3.2 Calculation of flow regulation and water mineralization (on
water-intake river stations and variants of WEB) |
From 3.2, 3.3.1, RD (on WR) and EIIF |
To 3.3.3, 3.3.4, 3.3.8 and 3.3.9 |
|
3.3.3 Calculation of water drawdowns to the downstream of a HPS
(over objects of the whole cascade) |
From 3.3.2, RD (on hydro-geology and WR) and EIIF |
To 3.3.4 |
|
3.3.4 Calculation of WEP of the cascade's HPS (by objects of the
whole cascade and variants of WEB) |
From 3.3.2, 3.3.3, RD (on parameters of HPS) and EIIF |
To 3.3.5, 3.3.6 and 3.3.8 |
|
3.3.5 Calculation of CEPE for HPS of the cascade (use of programs
1.2.1, 1.2.2 and 1.2.3) |
From 3.3.4, RD and EIIF |
To 3.3.6 and 3.3.8 |
|
3.3.6 Calculation of damage to energy due to change of the HPS'
regime (by compared variants of WEB) |
From 3.3.1, 3.3.4 and 3.3.5 |
To 3.3.10 |
|
3.3.7 Calculation of agricultural efficiency under irrigation WR
redistribution (by variants of the WEB) |
From 1.1, 3.2 and 3.3.1 |
To 3.3.10 |
|
3.3.8 Calculation of damage because of water evaporation off reservoirs'
impounded water level (by variants of the WEB) |
From 1.1, 3.3.2, 3.3.5 and RD (on evaporations) |
To 3.3.10 |
|
3.3.9 Calculation of damage because of irrigation water's mineralization
increase (by variants of the WEB) |
From 1.1, 3.2, 3.3.1 and 3.3.2 |
To 3.3.10 |
|
3.3.10 Calculation of summarizing effect over WEC, and selection
of an optimal variant of the WEB |
From 3.3.1, 3.3.6, 3.3.7, 3.3.8 and 3.3.9 |
Resulting
document |
