Volume 4 • Issue 4 • 1000152 J Civil Environ Eng ISSN: 2165-784X JCEE, an open access journal Wambua et al., J Civil Environ Eng 2014, 4:4 DOI: 10.4172/2165-784X.1000152 Review Article Open Access Drought Forecasting Using Indices and Artificial Neural Networks for Upper Tana River Basin, Kenya-A Review Concept Raphael M Wambua 1 *, Benedict M Mutua 1 and James M Raude 2 1 Department of Agricultural Engineering, Egerton University, Kenya 2 BEED, Jomo Kenyatta University of Agriculture and Technology, Kenya Abstract Due to increased impact of drought on water availability at different scales there is need to understand droughts especially in upper Tana River basin which is a critical and largest water system in Kenya. There is need to correlate trends of drought as infuenced by the climate variability of the present times. Drought frequency, duration and intensity in the basin have been increasing. The infuencing hydro-meteorological parameters and their interaction are necessary in developing measures for mitigating impacts of droughts. It is important to have a timely review of drought defnitions and fundamental concepts of droughts, classifcation of droughts, types of drought indices, historical droughts and artifcial neural networks with special focus of Kenyan a basin. Out of the review, this paper draws conclusions where gaps for more focused research especially for a typical river basin in Kenya exist. By developing effective drought forecasting tool for on-set detection and drought classifcation and drought forecasting, information on decision making on matters of drought preparedness and mitigation programmes will be available for proper water resources management. *Corresponding author: Raphael M Wambua, Department of Agricultural Engineering, Egerton University, Kenya, Tel: +254-723797872, E-mail: wambuarm@gmail.com Received June 03, 2014; Accepted July 29, 2014; Published August 06, 2014 Citation: Wambua RM, Mutua BM, Raude JM (2014) Drought Forecasting Using Indices and Artifcial Neural Networks for Upper Tana River Basin, Kenya-A Review Concept. J Civil Environ Eng 4: 152. doi:10.4172/2165-784X.1000152 Copyright: © 2014 Wambua RM, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Keywords: Upper Tana River basin; Drought frequency; Artifcial neural networks; Drought indices; Drought forecasting; Drought preparedness Introduction Drought is one of the critical natural disasters that adversely afect people, river basins, water resource systems and ecosystems [1]. It has been may be defned as a hydro-meteorological event on land characterized by temporary and recurring water scarcity. Te magnitude of the drought is indicated by extend with which it falls below a threshold level over an extended period of time [2]. Drought has been identifed as the most complex natural hazard since it is difcult to detect, develops slowly and impact on numerous aspects within a region [2]. Success of drought preparedness and mitigation depends upon timely information on its onset, and propagation in terms of temporal and spatial extent. Such information is usually obtained via efective and continuous drought monitoring using drought indices. Te study of spatial and temporal drought conditions is fundamental in ofering a wide range of solutions for control and management water resource systems. For instance, assessment of drought conditions is critical for planning water supplies, irrigation systems, crop and food security programmes, hydropower generation, water quality management and waste disposal systems [3]. Globally, drought has become more frequent and severe due to climate variability with diferent regions experiencing droughts at varying scales and times. Consequently, global impacts of drought on environmental, agricultural and socio-economic aspects need to be studied. As such, four distinct types of droughts namely; meteorological, agricultural, hydrological and socio-economic are recognised. Tese droughts have either direct or indirect impacts on river basins. Te former include degradation of water resources in terms of quantity and quality, reduced crop productivity, increased livestock and wildlife mortality rates, increased soil erosion and land degradation, and increased plant diseases and insect attacks [4,5]. Severe drought impacts have been experienced in other regions of the world leading to food insecurity and general increase in world food prices. For instance, very notable recent droughts of 2009 and 2011 in Kenya adversely afected the agricultural sector where crop yields were drastically reduced. Due to the problems mentioned above, river basin managers ofen have a challenge of addressing water risks, conficts and balancing economic development while at the same time maintaining reliable water resources [6]. African countries are among the most vulnerable to impacts of climate variability and drought. Te impacts adversely afect the well- being of the population. Tese impacts are compounded by numerous factors such as poverty, high population density, and human diseases. Tis is expected to multiply the demand for water, food and forage for livestock within the area in the next thirty years [6]. In East Africa, it has been projected that water availability will decline due to drought. In addition, there is a likelihood of increased desertifcation due to decline in precipitation especially during the dry months [7]. Droughts in Kenya have impacted adversely on rain fed agriculture, water resources, hydropower generation and ecosystems. Te agricultural sector alone which contributes to more than 51% of the gross domestic product (GDP) in Kenya [8] has been critically afected by frequent droughts. Over the past 50 years, Kenya has experienced at least one main drought per decade [9]. In addition, there has been a notable increase of drought in terms of frequency, duration and intensity. Any damage caused by drought on agriculture and water resources leads to famine, humanitarian crisis, rationing of water supply and decline in hydropower generation. Efective drought forecast allow water resource decision makers to develop drought preparedness plans. Such plans are critical for advance formulation of programmes to mitigate drought-related environmental, social and economic impacts. Terefore, accurate drought assessment and forecasting with an adequate lead time is paramount for formulation of mitigation measures in river basins [10]. Drought forecasting has received a new approach especially with J o u r n a l o f C i v il & E n v i r o n m e n t a l E n g i n e e r i n g ISSN: 2165-784X Journal of Civil & Environmental Engineering