In the theme Panta Rhei, this paper aims to develop a combined approach of data acquisition and a new semi-distributed non-stationary model taking into account land-use changes to reconstruct and predict annual runoff on an urban catchment in a data-sparse context. We use historical data and deploy a complementary short-term spatially-dense dedicated instrumentation. Applications were conducted on the tropical Mefou catchment (Yaoundé, Cameroon) to assess contributions of sub-catchments.
In the theme Panta Rhei, this paper aims to develop a combined approach of data acquisition and...
2LISAH, Univ Montpellier, INRA, IRD, SupAgro, Montpellier, France
3HSM, Univ Montpellier, CNRS, IRD, Montpellier, France
4Normandie Univ, UNIROUEN, UNICAEN, CNRS, M2C, Rouen, France
5GET, CNRS, IRD, University of Toulouse, Toulouse, France
6Institut de Recherches Géologiques et Minières, Centre de Recherches Hydrologiques, Yaoundé, Cameroon
7French National Research Institute for Development (IRD), Yaoundé, Cameroon
8WSP France, Toulouse, France
9Laboratoire de Géologie de l'ingénieur et d'Altérologie, Département des Sciences dela Terre et de l'Univers, Faculté des Sciences, Université de Yaoundé I, BP 812, Yaoundé, Cameroun
10Department of Earth Sciences, Faculty of Sciences, University of Ngaoundéré, Ngaoundere, Cameroon
11GM, Univ Montpellier, CNRS, Université des Antilles, Montpellier, France
†deceased
1OSU OREME, Univ Montpellier, Montpellier, France
2LISAH, Univ Montpellier, INRA, IRD, SupAgro, Montpellier, France
3HSM, Univ Montpellier, CNRS, IRD, Montpellier, France
4Normandie Univ, UNIROUEN, UNICAEN, CNRS, M2C, Rouen, France
5GET, CNRS, IRD, University of Toulouse, Toulouse, France
6Institut de Recherches Géologiques et Minières, Centre de Recherches Hydrologiques, Yaoundé, Cameroon
7French National Research Institute for Development (IRD), Yaoundé, Cameroon
8WSP France, Toulouse, France
9Laboratoire de Géologie de l'ingénieur et d'Altérologie, Département des Sciences dela Terre et de l'Univers, Faculté des Sciences, Université de Yaoundé I, BP 812, Yaoundé, Cameroun
10Department of Earth Sciences, Faculty of Sciences, University of Ngaoundéré, Ngaoundere, Cameroon
11GM, Univ Montpellier, CNRS, Université des Antilles, Montpellier, France
Received: 12 Mar 2019 – Accepted for review: 30 Apr 2019 – Discussion started: 02 May 2019
Abstract. Inter-tropical regions are nowadays faced to major land-use changes in data-sparse context leading to difficulties to assess hydrological signatures and their evolution. This work is part of the theme Panta Rhei of the IAHS, and aims to develop a combined approach of data acquisition and a new semi-distributed model taking into account land-use changes to reconstruct and predict annual runoff on an urban catchment. Applications were conducted on the Mefou catchment at Nsimalen (421 km2; Yaoundé, Cameroon) under rapid increase in urbanization since 1960. The data acquisition step combines an historical data processing and a short-term spatially-dense dedicated instrumentation (2017–2018), leading to 12 donor catchments, 6 from historical studies and 6 from the instrumentation presenting various topographic, soil and land-use characteristics. We developed an annual rainfall-runoff model based on mathematical relationships similar to the SCS model. The model needs the definition of a hydrological index I which is time variable and enables to take into account land-use changes and non-stationary relationships between rainfall and runoff. The index I is an empirical indicator defined as a combination of several components such as topography, soil, and land-use. The rules for the construction of I are obtained from data analysis on donor catchments. Then, the model was calibrated on donor catchments. Finally, two applications were conducted on eight target catchments composing the Mefou in order: (i) to study the spatial hydrological functioning and calculate the water balance during the short instrumentation period; (ii) to reconstruct the hydrograph at the Mefou and to simulate the impact of future scenarios of land-use and urbanization. Results show that that the Mfoundi catchment, integrating the three more urbanized sub-catchments, contributes near to 40 % of the Mefou despite covering only 23 % of the basin. The most urbanized sub-catchments present annual runoff coefficient about 0.86 against 0.24 for the most natural sub-catchments. The second result is the reconstruction of historical annual runoff from 1930–2017 with r2 = 0.68, RMSE = 99 mm and a mean absolute normalized error Ē = 14.5 % over the 29 observed years. The reconstruction of the annual runoff at Nsimalen confirms the moderate impact of urbanization on annual runoff before 1980. However, a decrease of about 50 % of the forest cover and an increase from 10 % to 35 % of the urban area between 1980 and 2017 are associated with an increase of 53 % of annual runoff coefficient for the Mefou at Nsimalen (0.44 against 0.29). Application for a fictive plausible scenario of urbanization in 2030 leads to an increase of more than 85 % of the annual runoff in comparison of the values observed in 1980. The coupled experimental-modelling approach proposed herein opens promising perspectives regarding the evaluation of the annual runoff in catchments under changes.
In the theme Panta Rhei, this paper aims to develop a combined approach of data acquisition and a new semi-distributed non-stationary model taking into account land-use changes to reconstruct and predict annual runoff on an urban catchment in a data-sparse context. We use historical data and deploy a complementary short-term spatially-dense dedicated instrumentation. Applications were conducted on the tropical Mefou catchment (Yaoundé, Cameroon) to assess contributions of sub-catchments.
In the theme Panta Rhei, this paper aims to develop a combined approach of data acquisition and...