Preprints
https://doi.org/10.5194/hess-2019-116
https://doi.org/10.5194/hess-2019-116
02 May 2019
 | 02 May 2019
Status: this preprint was under review for the journal HESS. A final paper is not foreseen.

A non-stationary model for reconstruction of historical annual runoff on tropical catchments under increasing urbanization (Yaoundé, Cameroon)

Camille Jourdan, Valérie Borrell-Estupina, David Sebag, Jean-Jacques Braun, Jean-Pierre Bedimo Bedimo, François Colin, Armand Crabit, Alain Fezeu, Cécile Llovel, Jules Rémy Ndam Ngoupayou, Benjamin Ngounou Ngatcha, Sandra Van-Exter, Eric Servat, and Roger Moussa

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.

This preprint has been withdrawn.

Camille Jourdan, Valérie Borrell-Estupina, David Sebag, Jean-Jacques Braun, Jean-Pierre Bedimo Bedimo, François Colin, Armand Crabit, Alain Fezeu, Cécile Llovel, Jules Rémy Ndam Ngoupayou, Benjamin Ngounou Ngatcha, Sandra Van-Exter, Eric Servat, and Roger Moussa

Interactive discussion

Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Interactive discussion

Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
Camille Jourdan, Valérie Borrell-Estupina, David Sebag, Jean-Jacques Braun, Jean-Pierre Bedimo Bedimo, François Colin, Armand Crabit, Alain Fezeu, Cécile Llovel, Jules Rémy Ndam Ngoupayou, Benjamin Ngounou Ngatcha, Sandra Van-Exter, Eric Servat, and Roger Moussa
Camille Jourdan, Valérie Borrell-Estupina, David Sebag, Jean-Jacques Braun, Jean-Pierre Bedimo Bedimo, François Colin, Armand Crabit, Alain Fezeu, Cécile Llovel, Jules Rémy Ndam Ngoupayou, Benjamin Ngounou Ngatcha, Sandra Van-Exter, Eric Servat, and Roger Moussa

Viewed

Total article views: 1,795 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
1,401 355 39 1,795 189 46 41
  • HTML: 1,401
  • PDF: 355
  • XML: 39
  • Total: 1,795
  • Supplement: 189
  • BibTeX: 46
  • EndNote: 41
Views and downloads (calculated since 02 May 2019)
Cumulative views and downloads (calculated since 02 May 2019)

Viewed (geographical distribution)

Total article views: 1,437 (including HTML, PDF, and XML) Thereof 1,417 with geography defined and 20 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 

Cited

Latest update: 02 Mar 2024
Download

This preprint has been withdrawn.

Short summary
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.