Vol.4, No.8A, 46-50 (2013) Agricultural Sciences
http://dx.doi.org/10.4236/as.2013.48A007
The rehabilitation of a reservoir: A new
methodological approach for calculating the
sustainable useful storage capacity
Annamaria De Vincenzo1, Bruno Molino2*
1School of Engineering, University of Basilicata, Potenza, Italy
2Department of Agricultural, Environmental and Food Sciences, University of Molise, Campobasso, Italy;
*Corresponding Author:
Received 28 May 2013; revised 25 June 2013; accepted 10 July 2013
Copyright © 2013 Annamaria De Vincenzo, Bruno Molino. This is an open access article distributed under the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited.
ABSTRACT
Present work introduces the sustainable useful
storage capacity as the minimum storage ca-
p acity able to satisfy the water dema nd for drink-
able, industrial and irrigational purposes and
necessary in order to overcome water deficit sit-
uations which, at least in Central Southern Italy,
occur in the summer, when agricultural demand
is really high. Sediment volumes to be removed
from the reservoir bottom will be calculated as
the difference between the current and the sus-
tainable useful storage capacities of the reser-
voir in study. The calculation methodology of
the useful sustainable storage capacity, based
on the reservoir water balance between inflows
at the reservoir and water demand, has been ap-
plied to the Camastra reservoir (Basilicata, Sou-
thern Italy), for which numerous reliable data in-
cluding more than 40 years of inflows and wa-
ter supplied volumes and data relative to 7 ba-
thymetric surveys are available. Result analysis
shows that this methodology, at least in the stu-
dy case, enables sediment quantities to be re-
moved more sustainably from a technical, eco-
nomical and environmental point of view.
Keyw ords: Reservoir Sedimentation; Water
Demand and Emergencies; Water Balance; Useful
Storage Capacity; R es e rvoir Sediment Reuse
1. INTRODUCTION
A dam impacts on the normal flow of water, creating
an upstream area with low water velocity and conse-
quently high sedimentation levels of sediments trans-
ported by the current. Over time these sediments lead to
a reduction in the initial storage capacity of the reservoir
bringing its progressive silting up. Because of their pre-
sence close to the dam these sediments could, in the
course of time, also constitute an impediment to the nor-
mal functioning of reservoir outlets for reservoir man-
agement as well as for control of floods ([1,2]).
The national regulatory framework concerning the
management of sediments is made up of a series of laws,
including laws 319/76, 183/89, 36/94, 152/99, D.M.30/
06/2004, 152/06 and the Environment Ministry Decree
n.161/2012, concerning the utilization of excavated earth
and rocks, which provide precise technical and organiza-
tional means for the safeguarding of waters and for the
defense of the soil, as well as for the management of
water resources and reservoir sedimentation.
Article 40, paragraph 2, of Decree Law 152/99 intro-
duces the obligation on the part of dam management to
draw up a “Management Project”.
The decree laws (still in force) necessary for the acti-
vation of the management projects were disciplined by
the decree of 30.06.2004.
The successive Decree Law 152/06, which is, at the
moment, the only operative tool supporting the drawing
up of management plans, once again highlighted the ne-
cessity for intervention on the question of the manage-
ment of these plants.
Specifically, article 114 of D. Law 152/06, which re-
placed art. 40 of D. Law 152/99 now abrogated, states
that actions dealing with sediment in reservoirs should be
carried out on the basis of a management project specific
for each reservoir which must:
 “Ensure the maintenance of reservoir capacity” (para-

A. De Vincenzo, B. Molino / Agricultural Sciences 4 (2013) 46-50 47
graph 2) through operations including draw-down,
dredging and flushing of the reservoirs which are en-
vironmentally sustainable and which do not impact
negatively on the river downstream from the reser-
voir;
 “Define the envisaged activity framework of these
operations”, which must also guarantee the function-
ing of dam outlets and intakes.
Basically the Management Project should provide a
detailed framework of envisaged activities including op-
erations draw-down, dredging and flushing connected
with plant maintenance; it will also include an activities
schedule and a description of the operating procedures
which the dam manager intends to utilize for the removal
of sediments and also its end use with the aim of restor-
ing the original reservoir capacity within the concession
deadline.
Reservoir management agencies are thus responsible,
according to the regulations in force, for the removal of
sediments, which, except in a limited number of cases,
are unsustainable in terms of quantity for the objective
technical and economic difficulties posed by sediment
removal operations and reuse ([3-5]).
The problem of the lack of sustainability with regard
to the restoration of the original useful capacity of reser-
voirs is particularly marked for the majority of Italian
reservoirs under public management in central-southern
Italy. Here, they usually have significant quantities of
sediment to deal with, lack of funds and technical, eco-
nomic and environmental difficulties associated with se-
diment disposal whereas lack of sustainability is only
marginally relevant for the hydro-electric plants in the
Alpine and pre-Alpine areas where, not surprisingly,
most of the management projects which have already
been presented, are located ([6,7]). The question of sus-
tainability becomes increasingly problematic, the greater
the ratio between existing levels of silting up and the
dead volume foreseen in the project. This ratio increases
when the annual average rate of silting up phenomena
differs from the constant average rate envisaged in the
project for the first decades of the plant life, for reasons
which are often not the responsibility of reservoir man-
agement Authority, such as absence of or delay in river
training works, modification in upstream land use (new
productive activities and consequent variations from
transported sediments to the river network), development
of landslide phenomena, etc.
The aim of the work is to propose a new methodology
for the computation of sustainable volumes of sediments
to be removed of the related sustainable useful storage
capacity. The proposed methodology takes into account
the users water demand rather than the restoration of the
original useful storage capacity imposed by law.
2. METHODOLOGY OF CALCULATION
The calculation methodology of useful sustainable ca-
pacity is founded on the analysis of monthly reservoir
water balance between inflows at the reservoir and water
demand, calculated on the basis of water volumes his-
torically supplied to reservoir users.
Inflows to the reservoir are calculated on the basis of
data annually elaborated by the reservoir management
Authority, from which it is possible to deduce for each
year the annual and monthly inflows by applying the
continuity equation to the storage. A successive statistical
elaboration ([8-11]) of the monthly inflows permits the
definition of laws of variation in the average monthly
inflow as a function of cumulative probability φ and,
thus, of the return period T. Figure 1 (where letters on x
axis are for the months of year) shows, for example, the
average monthly inflow I as a function of T at the
Camastra Dam (Basento River, Southern Italy).
The average monthly water volume supplied to users
U is also obtainable from historical data provided by the
reservoir management Authority and varies according to
the final utilization of the water resource (drinkable, in-
dustrial and irrigational uses). Between users the pro-
posed methodology also takes into account the water
course downstream from the dam which requires a mini-
mum ecological discharge for its conservation. Many
methods for the calculation of minimum ecological dis-
charge are available in the technical and scientific litera-
ture ([12-24]).
A monthly reservoir water balance between average
monthly inflows I, corresponding to a given return period,
and water volumes monthly supplied to users U and re-
leased for the river ecological preservation E, which are
constant in relation to the return period, permits the cal-
culation of the volumes W stored in the reservoir for each
month and for different return period according to the
equation:
Figure 1. Average monthly inflows from January (J) to De-
cember (D) as a function of return period.

A. De Vincenzo, B. Molino / Agricultural Sciences 4 (2013) 46-50
48
WIUE (1)
where
drink ind irr
UUU U (2)
Udrink, Uind and Uirr are the water volume supplied for
drinkable, industrial and irrigational purposes, respec-
tively.
If industrial and irrigation water supplies are carried
out, as usual, via stream bed discharge, like the minimum
ecological discharge, for each return period and each
month the stored volumes W are the result of the opera-
tion
drink indirr
WIUUU R  (3)
where R represent the instream releases dowstream from
the dam. The releases R will be equal to:
E in the months when (Uind + Uirr) = 0;
(Uind + Uirr) in the months when (Uind + Uirr) is greater
than E;
(E − Uind − Uirr ) in the months when (Uind + Uirr) is
lower than E.
Positive stored volumes indicate higher inflows with
respect to supplied volumes, whereas negative stored
volumes signify a deficit condition. The reservoir water
balance expressed by the relation (1) or (3) thus permits
the identification of possible periods of water deficit in
accordance with return period variation. In Italy the defi-
cit months fall usually under the summer season, when
water demand is greater than reservoir inflows. For each
return period the sum of the stored water volumes in the
deficit months represents the deficit volume


d
WT. If
the deficit volume is lower than the reservoir
current useful capacity C, which depends on the level of
silting up which the reservoir under study has experi-
enced over time, the current useful capacity is able to
overcome the water emergencies with a return period T
without any desiltation, dredging or sediment removing
operations. If otherwise > C will be necessary
to remove sediments from the reservoir bottom. The mi-
nimum sediment volume to be removed will be

d
WT
d
W
s

T

VT
 
sd
VTWT C (4)
In this way the sediment volumes to be removed are
calculated as a function of the users water demand and
water deficit situations which recur on average every T
years. When > C the sustainable useful capacity
will be

d
WT

s
CT
 
sd
CT WT (5)
which could in many cases be significantly lower than
the initial useful capacity and thus could result more
sustainable from a technical, economical and environ-
mental point of view.
3. THE CASE OF CAMASTRA DAM
The dam on the Camastra River, an affluent of the
Basento River, in Basilicata (Italy) (Figure 2), has a ba-
sin of 344 km2 and multiple resource purposes. At the
moment it has a silted up volume of more than 40% of
the initial useful volume, and thus is in a state of extreme
sufferance from this point of view. The Camastra dam
was also chosen because of the availability of large
quantities of reliable data including more than 40 years
of inflows and water supplied volumes and data relative
to at least 7 bathymetric surveys carried out in 13 years,
with an average of a survey every two years which is
practically unique in the Italian context.
In the case of the Camastra reservoir, the chronologi-
cal reconstruction of the silting up process was achieved
through an examination of the available bathymetric data
as well as by means of a precise analysis of the reservoir
hydrological management which led to obtaining data
relative to the maximum silting up possible until 1988
[25]. As shown in Ta b l e 1 the current amount of silting
Figure 2. Camastra reservoir river basin.
Table 1. Temporal evolution of silting up in the Camastra res-
ervoir.
year C (106 m3) V (106 m3) V (106 m3/year)
1967 35.172 0
0.333
1988 28.712 7
1.392
1993 21.754 6.958
0.489
1995 20.776 0.978
0.328
1997 20.120 0.656
0.087
2005 19.421 0.699

A. De Vincenzo, B. Molino / Agricultural Sciences 4 (2013) 46-50 49
up V in the Camastra reservoir is equal to about 16 × 106
m3 and the current useful capacity C is equal to 19.421 ×
106 m3.
As shown in [25] the average annual sedimentation
rate v is really high between 1988 and 1993 due to su-
perficial landslides confined on the Camastra reservoir
right bank. After 1993, a progressive decrease in sedi-
ment supply to the reservoir had occurred because of the
emptying of the landslides bodies and the effectiveness
of river training works and soil conservation practices
realized in the river network upstream the Camastra res-
ervoir.
4. APPLICATION TO THE CAMASTRA
DAM AND RESULTS DISCUSSION
The proposed methodology regarding the calculation
of useful sustainable capacity was applied to the case of
the Camastra reservoir. In the specific instance of the
Camastra reservoir reference was made to a minimum
ecological discharge of 100 l/s, corresponding to a dura-
tion of 358 days on the duration curve with T = 10 years.
As shown, for example, in the water balance carried
out by means of the Eq.3 for a return period equal to 10
years (Table 2), the water emergencies period of the
Camastra reservoir is from May to October and the defi-
cit volume is equal to 17.87 × 106 m
3. Like-
wise, the deficit volumes with T = 15 years and T = 20
years are equal to 20.78 × 106 m
3 and 22.40 × 106 m 3,
respectively.

10
d
W
As shown in Ta ble 3, with the current useful capacity
C estimated at 19.421 × 106 m
3, it is possible to over-
come water emergencies corresponding to return periods
Ta b l e 2 . Camastra reservoir water balance from January (J) to
December (D) for T = 10 years.
I Udrink Uind Uirr E R W
J 3 1.002 2.68 2.68−0.68
F 5 0.905 2.42 2.421.67
M 22.57 1.002 2.68 2.6818.89
A 12.74 0.969 2.59 2.599.18
M 6.15 1.002 1.607 0.572 2.68 0.502.47
J 2.27 0.969 1.101 1.2 2.59 0.28−1.29
J 0.48 1.545 1.533 2.702 2.68 0 −5.30
A 0.49 1.545 1.112 2.337 2.68 0 −4.50
S 0.96 1.496 0.931 1.698 2.59 0 −3.16
O 0.61 1.545 0.65 0.082 2.68 1.94−3.61
N 4.1 1.496 0.37 2.59 2.220.01
D 9.49 1.002 2.68 2.685.81
Table 3. Volume of sediments to be removed as a function of
the return period.
T
(years) Water deficit period Wd (106 m3) Vs (106 m3) C (106 m3)Cs (106 m3)
10 Jun-Oct 17.870 19.421 17.87
15 Jun-Nov 20.781.356 19.421 20.78
20 Jun-Nov 22.402.976 19.421 22.40
of 10 years; on the other hand the sediment volumes Vs
of at least one million and about three million cubic me-
ters should be removed in order to overcome water
emergencies corresponding to return periods of 15 and
20 years, respectively. The sustainable useful capacity Cs
is not so dissimilar from the current useful capacity C. If
the useful capacity was restored, according to the Italian
law requirements, to its initial value of 35.172 × 106 m3 it
would be necessary to remove more than 15 millions of
cubic metres of sediments from the reservoir bottom.
5. CONCLUSIONS
The proposed methodology regarding the calculation
of useful sustainable capacity was applied to the case of
the Camastra reservoir. In the specific instance of the
Camastra reservoir reference was made to a minimum
ecological discharge of 100 l/s, corresponding to a dura-
tion of 358 days on the duration curve with T = 10 years.
The proposed methodology is an instrument which al-
lows the rapid quantification of the volume of sediment
which is necessary to remove in changing scenarios, on
the condition of access to adequate quantities of reliable
bathymetric data; the scenarios are defined by:
 Return periods , which could, if necessary, be deter-
mined by a specific norm and which, as shown in the
Camastra case, have a significant influence on the
quantification of volumes;
 Water demand, which could remain unaltered or could
be modified in the future on the basis of users’ needs
and political decisions, but also in the light of possi-
ble benefits/economic profits deriving from the utili-
zation of the removed sediments.
This scientifically based approach could lead in many
cases including, for example, that of the Camastra reser-
voir, to volumes of sediments to remove which are sus-
tainable from a technical/economic viewpoint and also in
environmental terms (methods of desiltation and relative
impact on ecosystems downstream, final destination and
reuse of sediments, etc).
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