# Extreme Precipitation Indices Trend Assessment over the Upper Oueme River Valley-(Benin)

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## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Materials

#### 2.2. Methods

#### 2.2.1. Extreme Rainfall Indices

#### 2.2.2. Trends Detection

## 3. Results

#### 3.1. Trends in Frequency Indices

#### 3.2. Trends in Intensity Indices

## 4. Discussion

## 5. Conclusions

## Acknowledgments

## Author Contributions

## Conflicts of Interest

## Appendix A

**Figure A1.**Frequency indices evolution and trends in some stations studied (SS = Sen’s slope): (

**a**) R10m; (

**b**) R20m; (

**c**) R25m; (

**d**) CDD; and (

**e**) CWD.

## Appendix B

**Figure A2.**Intensity indices evolution and trends in some stations studied (SS = Sen’s slope): (

**a**) RX1day; (

**b**) RX5day; (

**c**) PRCPTOT; (

**d**) SDII; (

**e**) R95P; and (

**f**) R99P.

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Stations | Benin Meteo Agency Code | Long (Degree) | Lat (Degree) | Elevation (m) |
---|---|---|---|---|

Bassila | D037 | 1.667 | 9.017 | 384 |

Bembereke | D024 | 2.662 | 10.223 | 491 |

Beterou | D036 | 2.267 | 9.200 | 252 |

Birni | D026 | 1.517 | 9.983 | 430 |

Djougou | D030 | 1.662 | 9.692 | 439 |

Ina | D027 | 2.727 | 9.969 | 358 |

Kouande | D019 | 1.683 | 10.333 | 442 |

Okpara | D033 | 2.733 | 9.467 | 295 |

Parakou | D034 | 2.612 | 9.357 | 392 |

Tchaourou | D038 | 2.600 | 325 | 325 |

Indices | Name | Indices Calculation | Definition | Unit |
---|---|---|---|---|

Frequency Indices (adapted from WMO 2009) | ||||

R10mm | Number of heavy rainfall days | ${\mathrm{RR}}_{\mathrm{ij}}\ge 10\mathrm{mm}$ | Annual count of days when days rainfall ≥ 10 mm | Days |

R20mm | Number of very heavy rainfall days | ${\mathrm{RR}}_{\mathrm{ij}}\ge 20\mathrm{mm}$ | Annual count of days when days rainfall ≥ 20 mm | Days |

R25mm | Number of extremely heavy rainfall days | ${\mathrm{RR}}_{\mathrm{ij}}\ge 25\mathrm{mm}$ | Annual count of days when days rainfall ≥ 25 mm | Days |

CDD | Consecutive dry days | ${\mathrm{RR}}_{\mathrm{ij}}<1\mathrm{mm}$ | Maximum number of consecutive days with RR < 1 mm | Days |

CWD | Consecutive wet days | ${\mathrm{RR}}_{\mathrm{ij}}\ge 1\mathrm{mm}$ | Maximum number of consecutive days with RR $\ge $ 1 mm | Days |

Intensity Indices (adapted from WMO 2009) | ||||

RX1day | maximum Daily rainfall | $\mathrm{Rx}1{\mathrm{day}}_{\mathrm{j}}=\mathrm{max}({\mathrm{RR}}_{\mathrm{ij}})$ | Maximum 1-day Rainfall | mm |

RX5day | maximum 5-days rainfall | $\mathrm{Rx}5{\mathrm{day}}_{\mathrm{j}}=\mathrm{max}({\mathrm{RR}}_{\mathrm{ij}})$ | Maximum 5-days rainfall | mm |

PRCPTOT | Annual wet day rainfall total | ${\mathrm{PRCPTOT}}_{\mathrm{j}}={\displaystyle {\displaystyle \sum}_{\mathrm{i}=1}^{\mathrm{I}}}{\mathrm{RR}}_{\mathrm{ij}}$ | Annual total rainfall in wet day (RR > 1 mm) | mm |

SDII | Simple daily intensity index | ${\mathrm{SDII}}_{\mathrm{j}}=\frac{{\sum}_{\mathrm{w}=1}^{\mathrm{W}}{\mathrm{RR}}_{\mathrm{ij}}}{\mathrm{W}}$ | Annual mean rainfall when PRCP ≥ 1 mm | mm/day |

R95p | Very wet day | $\mathrm{R}95{\mathrm{P}}_{\mathrm{j}}={\displaystyle {\displaystyle \sum}_{\mathrm{w}=1}^{\mathrm{W}}}{\mathrm{RR}}_{\mathrm{wj}}$ | Annual total rainfall when RR > 95 percentile | mm |

R99p | Extremely wet day | $\mathrm{R}99{\mathrm{P}}_{\mathrm{J}}={\displaystyle {\displaystyle \sum}_{\mathrm{w}=1}^{\mathrm{W}}}{\mathrm{RR}}_{\mathrm{wj}}$ | Annual total rainfall when RR > 99 percentile | mm |

Stations | R10m | R20m | R25m | CDD | CWD | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

Z | p-Value | $\mathsf{\beta}$ | Z | p-Value | $\mathsf{\beta}$ | Z | p-Value | $\mathsf{\beta}$ | Z | p-Value | $\mathsf{\beta}$ | Z | p-Value | $\mathsf{\beta}$ | |

Bassila | −2.5 | 0.013 | −0.1467 | −1.6 | 0.105 | −0.0769 | −0.7 | 0.497 | −0.0217 | 4.9 | 7.59 × 10^{−}^{7} | 0.1398 | −1.5 | 0.133 | −0.183 |

Bembereke | −2.4 | 0.016 | −0.1079 | −2.3 | 0.023 | −0.075 | −1.7 | 0.089 | −0.0465 | −1 | 0.303 | −0.0253 | −1.8 | 0.066 | −0.126 |

Beterou | −0.5 | 0.626 | −0.0294 | 0.6 | 0.535 | 0.0278 | 0.7 | 0.510 | 0 | −1.1 | 0.270 | −0.0182 | 0.7 | 0.496 | 0.048 |

Birni | 1.8 | 0.071 | 0.0769 | 2.4 | 0.018 | 0.1111 | 1.6 | 0.120 | 0.0588 | 0.8 | 0.418 | 0.0171 | −1.5 | 0.124 | −0.138 |

Djougou | −0.2 | 0.825 | 0 | −1.2 | 0.241 | −0.0533 | −1.9 | 0.058 | −0.069 | −0.5 | 0.624 | 0 | 0.6 | 0.582 | 0.052 |

Ina | 0.1 | 0.949 | 0 | −0.3 | 0.05 | 0 | −0.4 | 0.718 | 0 | −0.5 | 0.605 | 0 | 0.9 | 0.391 | 0.071 |

Kouande | −2 | 0.044 | −0.0909 | −1.8 | 0.05 | −0.0625 | −1.4 | 0.156 | −0.0333 | 0.7 | 0.511 | 0 | −0.5 | 0.618 | −0.033 |

Okpara | −1.8 | 0.079 | −0.1042 | −1.1 | 0.276 | −0.0385 | −0.8 | 0.437 | 0 | 0.8 | 0.423 | 0.02 | −1.4 | 0.165 | −0.111 |

Parakou | −4 | 0.150 | −0.0682 | 0 | 0.963 | 0 | −0.7 | 0.485 | 0 | 0.1 | 0.926 | 0 | 1.1 | 0.291 | 0.075 |

Tchaourou | −0.7 | 0.497 | −0.031 | −0.6 | 0.558 | −0.0235 | −0.4 | 0.693 | 0 | −0.3 | 0.771 | 0 | 0 | 0.972 | 0 |

Indices | Significant Positive Trend (%) | No Significant Positive Trend (%) | Significant Negative Trend (%) | No Significant Negative Trend (%) |
---|---|---|---|---|

R10mm | 0 | 20 | 30 | 50 |

R20mm | 10 | 10 | 10 | 70 |

R25mm | 0 | 20 | 0 | 80 |

CWD | 0 | 40 | 0 | 60 |

CDD | 10 | 40 | 0 | 50 |

Stations | RX1day | RX5day | PRCPTOT | SDII | R95P | R99P | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

Z | p-Value | $\mathsf{\beta}$ | Z | p-Value | $\mathsf{\beta}$ | Z | p-Value | $\mathsf{\beta}$ | Z | p-Value | $\mathsf{\beta}$ | Z | p-Value | $\mathsf{\beta}$ | Z | p-Value | $\mathsf{\beta}$ | |

Bassila | −2.7 | 0.008 | −0349 | −1.7 | 0.083 | −0.288 | −2.5 | 0.012 | −4.24 | 0,3 | 0.741 | 0.011 | −3.8 | 0.0001 | −1.268 | −1.8 | 0.072 | −0.257 |

Bembereke | −2 | 0.044 | −0.277 | −1.4 | 0.169 | −0.281 | −2.5 | 0.013 | −3.89 | −1.4 | 0.159 | −0.025 | −2.4 | 0.016 | −1.195 | −2 | 0.044 | −0.277 |

Beterou | 0.4 | 0.662 | 0.083 | 0.5 | 0.627 | 0.107 | 0.4 | 0.715 | 0.775 | −0.1 | 0.932 | −0.0007 | 0.6 | 0.535 | 0.344 | 0.7 | 0.508 | 0.106 |

Birni | −0.5 | 0.634 | −0.045 | 0.1 | 0.954 | 0 | 0.6 | 0.574 | 1.039 | 2.3 | 0.021 | 0.053 | −0.07 | 0.397 | −0.208 | 0 | 0.972 | 0 |

Djougou | −0.2 | 0.876 | −0.012 | −0.3 | 0.749 | −0.067 | −0.7 | 0.513 | −1.04 | −2 | 0.044 | −0.030 | 0.3 | 0.772 | 0.105 | 1.1 | 0.263 | 0.167 |

Ina | −3.5 | 0.0005 | −0.483 | −2.2 | 0.028 | −0.39 | −0.3 | 0.754 | −0.46 | −2.2 | 0.025 | −0.031 | −1.6 | 0.103 | −0.601 | −1.2 | 0.246 | −0.138 |

Kouande | 0.1 | 0.958 | 0.006 | 0.9 | 0.382 | 0.209 | −1.6 | 0.119 | −2.38 | −1.2 | 0.224 | −0.016 | 0.3 | 0.749 | 0.116 | −0.2 | 0.830 | −0.021 |

Okpara | 1 | 0.323 | 0.180 | −0.6 | 0.522 | −0.15 | −1.3 | 0.209 | −2.37 | −0.3 | 0.768 | −0.004 | −0.4 | 0.671 | −0.189 | 0.7 | 0.509 | 0.1412 |

Parakou | 2.1 | 0.039 | 0.326 | 0.4 | 0.694 | 0.0672 | −0.4 | 0.715 | −0.45 | −0.4 | 0.668 | −0.008 | 1.7 | 0.082 | 0.827 | 2.2 | 0.026 | 0.3544 |

Tchaourou | −0.1 | 0.903 | −0.018 | −0.3 | 0.754 | −0.065 | −0.5 | 0.647 | −0.75 | −0.6 | 0.524 | −0.013 | −0.8 | 0.404 | −0.436 | 0.5 | 0.626 | 0.064 |

Indices | Significant Positive Trend (%) | No Significant Positive Trend (%) | Significant Negative Trend (%) | No Significant Negative Trend (%) |
---|---|---|---|---|

RX1day | 10 | 30 | 30 | 30 |

RX5day | 0 | 40 | 10 | 50 |

PRCPTOT | 0 | 20 | 20 | 60 |

SDII | 10 | 10 | 20 | 60 |

R95P | 0 | 40 | 20 | 40 |

R99P | 10 | 40 | 10 | 40 |

© 2017 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

André Attogouinon, A.; Lawin, A.E.; M’Po, Y.N.; Houngue, R.
Extreme Precipitation Indices Trend Assessment over the Upper Oueme River Valley-(Benin). *Hydrology* **2017**, *4*, 36.
https://doi.org/10.3390/hydrology4030036

**AMA Style**

André Attogouinon A, Lawin AE, M’Po YN, Houngue R.
Extreme Precipitation Indices Trend Assessment over the Upper Oueme River Valley-(Benin). *Hydrology*. 2017; 4(3):36.
https://doi.org/10.3390/hydrology4030036

**Chicago/Turabian Style**

André Attogouinon, André, Agnidé E. Lawin, Yèkambèssoun N’Tcha M’Po, and Rita Houngue.
2017. "Extreme Precipitation Indices Trend Assessment over the Upper Oueme River Valley-(Benin)" *Hydrology* 4, no. 3: 36.
https://doi.org/10.3390/hydrology4030036