No. 11337
FRANCE
and
SPAIN
Agreement relating to Lake Lanoux (with an arrangement
concerning the lake's development). Signed at Madrid
on 12 July 1958
Exchange of letters constituting an agreement amending the
above-mentioned arrangement. Paris, 27 January 1970
Authentic texts: French and Spanish.
Registered by France on 21 September 1971.
FRANCE
et
ESPAGNE
Accord relatif au lac Lanoux (avec rglement concernant
ľaménagement de ce dernier). Signé  Madrid le 12
juillet 1958
Échange de lettres constituant un accord modifiant le rglement
susmentionné. Paris, 27 janvier 1970
Textes authentiques : français et espagnol.
Enregistrés par la France le 21 septembre 1971.
1971 Nations Unies -- Recueil des Traités 235
[TRANSLATION TRADUCTION]
AGREEMENT1 BETWEEN THE GOVERNMENT OF THE
FRENCH REPUBLIC AND THE SPANISH GOVERN
MENT RELATING TO LAKE LANOUX
AGREEMENT RELATING TO LAKE LANOUX
The Government of the French Republic and the Spanish Government,
Considering the Lake Lanoux water use project, of which the Governor
of the Province of Gerona was notified by the Prefect of the Pyr n esOrientales
on 21 January 1954;
The proposals submitted on 12 December 1955 by the French delegation
to the Ad Hoc Joint Commission established to prepare a project for the
development of the waters of Lake Lanoux;
The award rendered on 16 November 1957 by the Court of Arbitration
charged with ruling upon the interpretation of the Treaty of Bayonne of
26 May 1866 and of the Additional Act of the same date concerning the use
of the waters of Lake Lanoux,
Have agreed on the following provisions :
Article 1
Electricit de France shall effect return delivery, through the Ari geCarol
gallery, of a quantity of water equal to the natural flow diverted from
the Carol basin, the minimum annual amount to be returned being fixed at
20 million cubic metres.
Electricit de France shall install in the reservoir the necessary outlet
works to provide for outflow into the Carol in the event ofan incident ofany
kind preventing return delivery via the Ari ge.
Electricit de France shall install all requisite measuring devices to
ensure that the full return flow is steadily maintained.
The technical procedures for implementing this article shall be laid down
in the Arrangement annexed to this Agreement.
1 Came into force on 12 July 1958 by signature.
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236 United Nations -- Treaty Series 1971
Article 2
A Joint Commission shall supervise the implementation of the measures
referred to in the preceding article. The Commission shall be composed of
six members, three appointed by the Spanish Government and three by the
French Government.
The Commission shall be presided over by the Chairman of the Spanish
delegation and the Chairman of the French delegation in turn, for periods of
one year each. During the first year, chairmanship of the Commission shall
be held by the Spanish delegation.
Article 3
The Commission shall meet at the request of either delegation, and
upon being convened by its Chairman, as often as may be necessary and in
any event not less than once each year, in mid-July. Its reports and the
records of its meetings shall be transmitted to the two Governments.
Article 4
In time of construction, the Commission shall supervise the execution
of work relating to the installations and devices referred to in article 1.
In time of operation, the Commission shall ensure that the return flow is
steadily maintained.
The Commission shall be provided with the means and facilities neces
sary for the performance of its duties.
Article 5
The Spanish Government may notify the French Government of the
name of an official serving at its Consulate in Toulouse who may be a repre
sentative of the Ebro Hydrographie Confederation and who shall have free
access at all times to any of the installations of the concession referred to in
article 1.
This official shall enjoy the immunities and privileges provided for in the
Franco-Spanish Consular Convention of 7 January 1862.
Reports of the said official shall be transmitted to the Commission.
Article 6
The Commission shall inform the two Governments of any contra
ventions of the provisions of article 1 which may come to its attention.
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1971 Nations Unies -- Recueil des Traités 237
The French Government shall take all appropriate steps to ensure the
cessation ofsuch contraventions and, where necessary, to compensate for the
damage caused.
Article 7
Any dispute which may arise between the two Governments regarding
the application of the foregoing provisions shall be settled in accordance
with the procedure laid down in the Arbitration Convention of 10 July 1929. x
Madrid, 12 July 1958
Ambassador of France : Minister for Foreign Affairs :
LA TOURNELLE FERNANDO CASTIELLA
DEVELOPMENT OF LAKE LANOUX
ARRANGEMENT REFERRED TO IN ARTICLE 1 OF THE AGREEMENT
Water diverted from the Lanoux natural catchment basin to the Hospitalet falls
is drawn off from the flow of the Carol. The flow thus diverted shall be returned to
the Carol through a gallery approximately five kilometres in length, the "Ari geCarol
gallery" ; water from the Ari ge shall be directed through an intake situated at
elevation 1575 metres into the said gallery, which shall be of sufficient capacity to
ensure a flow of five cubic metres per second. Such water shall be returned to the
Carol before the border, downstream of the village of Port .
I. Principles governingflow determination
The volume of water diverted from the Carol at Lake Lanoux and the volume
returned through the Ari ge-Carol gallery shall be metered continuously by means
of a series of measuring devices. Such devices shall be installed in pairs, with the aim
of enhancing the accuracy of the measurements and in order to guard against any
failure of one of the instruments (see Plan Lt 8-26 annexed hereto).2
1. Divertedflow
This comprises water from the Lanoux catchment basin and from the streams of
Fourats, la Porteille and Courtal-Rousso, which are tributaries of the Font-Vive.
If:
A=gravity flow from the Carol,
P = pumped flow from tributaries of the Ari ge, and
T = turbine flow,
t>ese being the total quantities for any given measurement period, and
Vr=the corresponding variation in reservoir storage,
1 League of Nations, Treaty Series, vol. CXLVIII, p. 369.
2 The Government of France indicated, in agreement with the Government of Spain, that this plan
was not to be considered as an integral part of the Agreement.
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238 United Nations -- Treaty Series 1971
Then:
Vr=A + P-T,
and hence A = V> P+T.
For the purpose of determining quantities P and T, two Venturi meters one
for each direction offlow shall be installed in the Lanoux penstock, on either side
of the head gates. The measuring instruments of the said meters shall be activated
or de-activated, according to the direction of the current, by a special automatic
detector. They shall be equipped with a totalizer for turbine flow or pumped flow.
V> shall be deduced from the curve showing the storage capacity in terms of the
stage of the Lake, the stage being measured by a high-precision pressure gauge.
During the period 15 June-15 September, flow shall be increased by 70,000 cubic
metres per month in order to take account of evaporation from the enlarged surface
area of the Lake.
2. Return delivery
Return delivery shall normally be effected through the Ari ge-Carol gallery;
the intake has been so designed as to enable flow to be regulated to within five cubic
metres per second. If necessary, the requisite return flow may be supplied directly
through the Font-Vive gallery, whatever the water level in the reservoir, by means of
a hollow-jet valve situated near the Lanoux distribution room.
A Venturi flume shall be installed at the downstream mouth of each of the said
galleries. Flow shall be measured and totalized by a precision instrument.
A measuring device shall also be installed at the upstream mouth of the Ari geCarol
gallery for the purpose of flow regulation.
II. Principles ofoperation
The period between 1 September of one year and 31 August of the following
year inclusive shall be deemed to constitute the water year.
The various kinds of flow shall normally be computed on a weekly basis.
A quantity ofwater equivalent to the yield diverted over a one-week period shall
normally be delivered during the following week at a steady rate of flow with a
permissible deviation ofplus or minus 10 per cent.
Total surpluses or shortfalls in weekly return deliveries, excluding surplus
quantities over and above the permissible deviation of 10 per cent, must be com
pensated every four weeks, such water to be restored during the fifth week at a steady
rate of flow and in accordance with the accumulated readings taken between the
beginning and end of the said four-week period.
The quantity ofwater which may still be required to attain delivery ofthe guaran
teed minimum annual flow of 20 million cubic metres shall be computed on 15 July
of each year; any shortfall of water shall be delivered at a steady rate of flow during
the second half of July and the month of August, the adjustments necessary to take
account of the natural flow being made every fortnight.
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1971 Nations Unies -- Recueil des Traités 239
The Supervisory Commission provided for in article 2 ofthe Agreement relating
to Lake Lanoux shall meet in mid-July each year in order to establish specific pro
cedures to ensure the minimum annual guaranteed return flow, taking into account
the probable summer yield.
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240 United Nations Treaty Series 1971
EXCHANGE OF LETTERS CONSTITUTING AN AGREE
MENT 1 BETWEEN FRANCE AND SPAIN AMENDING
THE ARRANGEMENT OF 12 JULY 19582 RELATING
TO LAKE LANOUX
MINISTRY OF FOREIGN AFFAIRS
Paris, 27 January 1970
Sir,
At its meeting of 28 September 1965, the Joint Franco-Spanish Super
visory Commission for the development of Lake Lanoux proposed that the
text ofthe Arrangement referred to in article 1 of the Franco-Spanish Agree
ment of 12 July 19582 relating to Lake Lanoux, and annexed to that Agree
ment, should be amended.
The Commission proposes the following new text for the Arrangement :
Water diverted from the Lanoux natural catchment basin to the Hospitalet falls
is drawn offfrom the flow ofthe Carol. The flow thus diverted shall be returned to the
Carol through a gallery approximately five kilometres in length, the " Ari ge-Carol
gallery " ; water from the Ari ge shall be directed through an intake situated at eleva
tion 1575 metres into the said gallery, which shall be of sufficient capacity to ensure
a flow offive cubic metres per second. Such water shall be returned to the Carol before
the border, downstream of the village of Port .
I. Principles governingflow determination
The volume of water diverted from the Carol at Lake Lanoux and the volume
returned through the Ari ge-Carol gallery shall be metered continuously by means of
a series of measuring devices. Such devices shall be installed in pairs, with the aim of
enhancing the accuracy of the measurements and in order to guard against any
failure of one of the instruments.
1. Divertedflow
This comprises water from the Lanoux catchment basin and from the streams of
Fourats, la Porteille and Courtal-Rousso, which are tributaries of the Font-Vive.
1 Came into force on 27 January 1970 by the exchange of the said letters.
2 See p. 235 of this volume.
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1971 Nations Unies -- Recueil des Traités 241
If:
A=gravity flow from the Carol,
P = pumped flow from tributaries of the Ari ge, and
T = turbine flow,
these being the total quantities for any given measurement period, and
Vr=the corresponding variation in reservoir storage,
It follows that Vr = A + P-T and A=Vr-P+T.
For the purpose of determining quantities P and T, two Venturi meters one
for each direction of stream flow shall be installed in the Lanoux penstock, on
either side of the head gates. The measuring instruments of the said meters shall be
activated or de-activated, according to the direction of the current, by a special
automatic detector. They shall be equipped with a totalizer forturbine flow or pumped
flow.
Vr shall be deduced from the curve showing the storage capacity in terms of the
stage of the Lake, the stage being measured by a high-precision pressure gauge.
During the period 15 June-15 September, flow shall be increased by 70,000 cubic
metres per month in order to take account of evaporation from the enlarged surface
area of the Lake.
2. Return delivery
Return delivery shall normally be effected through the Ari ge-Carol gallery ; the
intake has been so designed as to enable flow to be regulated to within five cubic
metres per second. If necessary, the requisite return flow may be supplied directly
through the Font-Vive gallery, whatever the water level in the reservoir, by means of
a hollow-jet valve situated near the Lanoux distribution room.
A Venturi flume shall be installed at the downstream mouth of each of the said
galleries. Flow shall be measured and totalized by a precision instrument.
A measuring device shall also be installed at the upstream mouth of the Ari geCarol
gallery for the purpose of flow regulation.
II. Principles ofoperation
It is hereby agreed that diverted flow and return flow shall be equalized each
year within the annual accounting periods stipulated below :
In the case of diverted flow, the water year shall be established as the following
period: 1 September of a given year to 31 August of the following year.
In the case of return flow, the water year shall be the period 1 May-30 April
following the start of the water year for diverted flow.
Where less than 20 million cubic metres ofwater are diverted from Lake Lanoux
in any given water year, the return flow to be effected during the corresponding water
year shall be not less than 20 million cubic metres.
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242 United Nations -- Treaty Series 1971
Technicalproceduresfor implementation
Return delivery shall be effected through the Ari ge-Carol gallery from the
beginning of May onwards. It shall be continued until the diverted flow is fully com
pensated. The rate of flow through the gallery may be reduced, except in July and
August, in order to limit the extent of any temporary surplus of return flow over
diverted flow.
Where, in exceptional circumstances, the requisite compensation has not been
made by 30 September :
(a) In the case of a shortfall, return delivery shall be maintained during the months
of October, November, March and April, with a break during the months of
December, January and February. However, where the minimum quantity of
20 million cubic metres has still not been restored, return delivery shall be main
tained without interruption until that figure is reached.
(b) In the case of a surplus, compensation shall be made during the following year,
the excess quantities delivered during the previous year being deducted from the
return flow due to be effected during the current year.
In such a case, return delivery shall not commence until such time as the flow
which would normally have been drawn off from the Ari ge during the intervening
period equals the amount of the surplus.
In these circumstances as well, a minimum return flow of20 million cubic metres
shall be assured.
Unforeseen difficulties
Acting at the request of either delegation, the Joint Supervisory Commission
shall settle any difficulties of implementation which may arise, taking into account
the above principles and methods, on which return delivery arrangements must be
based. To this end, the situation shall be reviewed at one of the annual meetings.
The French Government for its part approves the Commission's
proposal.
Ifthis proposal also meets with the approval ofthe Spanish Government,
I have the honour to suggest that this letter and your reply thereto should
constitute a formal agreement between our two Governments on the new
text for the Arrangement.
I further suggest that this text should enter into force on the date of the
exchange of this letter and your reply thereto.
Accept, Sir, etc.
AUGUSTIN JORDAN
Minister Plenipotentiary
Department of Economic and Financial Affairs
General Affairs
His Excellency Mr. Cortina y Mauri
Ambassador of Spain
Paris
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II
EMBASSY OF SPAIN IN PARIS
Paris, 27 January 1970
Sir,
I have the honour to acknowledge receipt of your letter of today's date,
reading as follows :
[See letter I]
ir to infor
f the Spar
Accept, Sir, etc.
I have the honour to inform you that the provisions of the above letter
have the agreement of the Spanish Government.
Mr. Augustin Jordan
Minister Plenipotentiary
Ministry of Foreign Affairs
Paris
[Signed]
PEDRO CORTINA
N0 11337