David Walker

David Walker
Wageningen University & Research | WUR · Water Resources Management group

Doctor of Philosophy

About

24
Publications
8,804
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
269
Citations
Additional affiliations
November 2020 - present
Wageningen University & Research
Position
  • PostDoc Position
September 2019 - October 2020
Kyushu University
Position
  • PostDoc Position
April 2018 - June 2019
Newcastle University
Position
  • PostDoc Position

Publications

Publications (24)
Article
Full-text available
Drought monitoring and early warning systems (DEWSs) are seen as helpful tools to tackle drought at an early stage and reduce the possibility of harm or loss. They usually include indices attributed to meteorological, agricultural and/or hydrological drought: physically based drought drivers. These indices are used to determine the onset, end and s...
Article
Full-text available
Drought management is currently informed by a variety of approaches, mostly responding to drought crisis when it happens. Toward more effective and integrated drought management, we introduce a conceptual drought diagnosis framework inspired by diagnostic concepts from the field of medicine. This framework comprises five steps: 1. Initial diagnosti...
Preprint
The São Francisco River (SFR) flow has been partially transferred to dryland catchments in Northeastern Brazil (NEB), to help deal with recurrent regional water shortages. However, the influence of this water transfer on overexploited aquifer systems had not been investigated. Our goal was to assess the groundwater recharge and the potential of the...
Article
Full-text available
Drought‐affected regions often contain high densities of small reservoirs, usually informally built, as drought‐coping mechanism. These structures influence socio‐hydrological dynamics and have the potential to alter hydrological processes relevant to drought emergence and development. This study aimed to analyze the influence of a high concentrati...
Article
Full-text available
The hydrological impact of many expensive investments on watershed interventions remains unquantified due to lack of time series data. In this study, remote sensing imagery is utilized to quantify and detect vegetation cover change in Magera micro-watershed, Ethiopia, where sustainable land management interventions have been implemented. Normalized...
Article
Full-text available
Citizen science is blossoming in the water sciences and benefits to the scientific community are well reported. The experiences of involved citizens are less well researched, however, particularly in the Global South. To address this knowledge gap, we investigated the participant motivations of citizen science water projects in Nepal and the benefi...
Preprint
Full-text available
Drought monitoring and Early Warning Systems (DEWS) are seen as helpful tools to tackle drought at an early stage and reduce the possibility of harm or loss. They usually include indices attributed to meteorological, agricultural and/or hydrological drought: physically based drought drivers. These indices are used to determine the onset, end and se...
Article
Full-text available
Citizen science is proliferating in the water sciences with increasing public involvement in monitoring water resources, climate variables, water quality, and in mapping and modeling exercises. In addition to the well‐reported scientific benefits of such projects, in particular solving data scarcity issues, it is common to extol the benefits for pa...
Article
Full-text available
The groundwater of volcanic aquifers, dissected by various structures and affected by several volcanic eruption events, varies in quality. A large number of rural people depend on shallow aquifers tapped by shallow hand wells and springs. On the other hand, the urban population is dependant on deep aquifers using drilled boreholes. The location of...
Article
Full-text available
Volcanic aquifers are sources of groundwater for both urban and rural areas. Their occurrence in geological formations and water quality are the main issues for sustainable utilisation. Dangila town and its surrounding area, northwest Ethiopia, is assessed for hydrogeological framework and groundwater quality based on well and hydrochemical data. T...
Article
Understanding recharge processes is fundamental to improve sustainable groundwater resource management. Shallow groundwater (SGW) is being developed for multiple purposes in Ethiopia without consideration of monitoring. We established a citizen science-based hydro-meteorological monitoring network, with a focus on SGW recharge estimation, in Eshito...
Article
Full-text available
We present an evidence-based approach to identify how best to support development of groundwater for small-scale irrigation in sub-Saharan Africa (SSA). We argue that it is important to focus this effort on shallow groundwater resources. We demonstrate and test this proposal at a case study site: Dangila woreda in the north-western highlands of Eth...
Book
Full-text available
This guideline is the second part of a two-part series concerning citizen science hydroclimate monitoring. The two guidelines were designed to be simultaneously consulted though the first is focused particularly on Ethiopia. The documents have been developed following citizen science research in Ethiopia since 2014 and in India since 2016 where mul...
Article
Full-text available
Rural communities in sub-Saharan Africa commonly rely on shallow hand-dug wells and springs; consequently, shallow aquifers are an extremely important water source. Increased utilisation of shallow groundwater could help towards achieving multiple sustainable development goals (SDGs) by positively impacting poverty, hunger, and health. However, the...
Article
Full-text available
Ephemeral sand rivers are common throughout the world's dryland regions, often providing a water source where alternatives are unavailable. Alluvial aquifer recharge results from rare surface water flows. Assessment of surface flow frequency using traditional methods (rain or flow gauges) requires a high-density monitoring network, which is rarely...
Book
Full-text available
This document provides the first guideline to inform community-based monitoring (CBM) implementation in Ethiopia. It has been developed following citizen science research in Ethiopia since March 2014, where multiple study sites have had CBM implemented using an iterative process leading to continual improvement of the methodology. In addition, the...
Article
Full-text available
Study region: Molototsi sand river, Limpopo, South Africa. Study focus: Ephemeral sand rivers are common throughout the world's dryland regions, often providing a water source where more conventional sources are unavailable. However, these alluvial aquifers are poorly represented in the literature. Extensive field investigations allowed estimation...
Article
Full-text available
Although most recharge estimation studies apply multiple methods to identify the possible range in recharge values, many do not distinguish clearly enough between inherent uncertainty of the methods and other factors affecting the results. We investigated the additional value that can be gained from multi‐method recharge studies through insights in...
Conference Paper
Full-text available
Pumping tests have been successfully conducted on shallow hand-dug wells in two areas of northwest Ethiopia. The drawdown and recovery data were analysed separately providing consistent results confirming suitability of methods. Hydraulic conductivity estimates ranged from 0.2 to 6.4 m/d (mean = 2.3 m/d, median = 1.6 m/d) in the dry season and rang...
Article
Full-text available
This study shows how community-based hydrometeorological monitoring programmes can provide reliable high-quality measurements comparable to formal observations. Time series of daily rainfall, river stage and groundwater levels obtained by a local community in Dangila woreda, northwest Ethiopia, have passed accepted quality control standards and hav...
Article
Full-text available
There is a need for an evidence-based approach to identify how best to support development of groundwater for small scale irrigation in sub-Saharan Africa (SSA). We argue that it is important to focus this effort on shallow groundwater resources which are most likely to be used by poor rural communities in SSA. However, it is important to consider...

Questions

Question (1)
Question
Anyone researching flash droughts? Or are you from a part of the world where short duration dry spells have negative impacts (what do you call them and what are the impacts)? Please help us out by completing this 2-min survey: https://louisecsc.typeform.com/to/pbjYGKZZ
Thank you

Network

Cited By

Projects

Projects (2)
Project
Project Aim: To develop improved understanding of shallow groundwater resources and their vulnerability to climate variability, land use change and increased abstraction. I will also evaluate the information needs and feasible methods for assessing shallow groundwater resources across sub-Saharan Africa. The principal research is being conducted for two field sites; near Dangila in Amhara region of Ethiopia and near Giyani in Limpopo province of South Africa respectively. The research involves field hydrogeological investigations (surveys of wells, springs and rivers; surface and groundwater sampling for chemistry, stable isotope and radon-222 analysis; ground-truthing satellite imagery; pumping and recovery tests on hand dug wells; river flow-gauging; geological surveys; etc), recharge assessments, and numerical modelling; including simulation of future changes to climate and land use. Much of the data required for the numerical modelling is collected from a community-based monitoring programme. Groundwater in much of rural Sub-Saharan Africa is only just beginning to be utilised for irrigation rather than relying on rains. It is thought, as occurred in south Asia, that an increase in the use of groundwater, converting subsistence smallholders into market farmers, could have a profoundly positive impact on poverty alleviation and gender equality. The project is in collaboration with the International Water Management Institute (IWMI).