A novel sediment fingerprinting method using filtration: application to the Mara River, East Africa
- 522 Downloads
Sediment fingerprinting with elemental tracers is widely used to identify sources of sediment to rivers. However, due to the need to isolate large amounts of suspended sediment, this approach can be difficult to implement in remote locations, such as the Mara River in Kenya, where high (and increasing) sediment loads are of concern.
Materials and methods
We report several innovations that allowed us to carry out sediment fingerprinting in a portion (>6,500 km2) of the Mara River Basin. First, we utilized sediment-laden filters (sediment mass ∼0.1 g) for our river samples, rather than the traditional approach of extracting >1 g of sediment from large volumes of water. This allowed us to easily collect flow-weighted samples, and to process and analyze samples without access to centrifugation equipment. We carried out extensive quality control tests to ensure that we could reproducibly measure elemental concentrations of sediment trapped on filters. Second, we modified a readily available Bayesian inference mixing model (Stable Isotope Analysis in R) to create source signatures and to apportion downstream samples to sources. Third, we included hippo feces as a potential source, given the critical role that large wildlife plays in this ecosystem.
Results and discussion
We found that: (1) sediment captured by filtration can be digested and analyzed reproducibly and used in sediment fingerprinting; (2) our four sources (three geographic categories and hippo feces) were reasonably well-separated in their signatures; (3) the three sub-basins all contributed substantially to sediment loading in the Mara; and (4) hippo feces contributed a small, but measurable, proportion of sediment in this system.
Sediment-laden filters can be used successfully in identifying sediment sources through fingerprinting. The modified method of sediment fingerprinting should prove useful in other remote river basins. Our results support the hypothesis that the Upper Mara is important in supplying sediments to the river, while also highlighting the Talek sub-basin as a major contributor.
KeywordsBayesian mixing model East Africa Filtration Hippopotamus Sediment fingerprinting
- Dutton CL (2012) Sediment fingerprinting in the Mara River Basin; Uncovering relationships between wildlife, tourism and non-point source pollution. MESc Thesis. Yale University School of Forestry and Environmental Studies, New Haven, CT, USAGoogle Scholar
- Edwards TK, Glysson GD (1999) Field Methods for Measurement of Fluvial Sediment. In: Techniques of Water-Resources Investigations of the U.S. Geological Survey. Reston, Virginia, USA, p 97Google Scholar
- Evrard O, Navratil O, Ayrault S, Ahmadi M, Nemery J, Legout C, Lefevre I, Poirel A, Bonte P, Esteves M (2011) Combining suspended sediment monitoring and fingerprinting to determine the spatial origin of fine sediment in a mountainous river catchment. Earth Surf Process Landf 36:1072–1089CrossRefGoogle Scholar
- Gellis AC, Walling DE (2011) Sediment source fingerprinting (tracing) and sediment budgets as tools in targeting river and watershed restoration programs. In: Stream Restoration in Dynamic Fluvial Systems: Scientific Approaches, Analyses, and Tools, vol 194. Geophys. Monogr. Ser. AGU, Washington, DC, USA, pp 263–291Google Scholar
- Goddard DL (2011) Data validation standard operating procedures for contract laboratory program inorganic data by inductively coupled plasma–atomic emission spectroscopy and inductively coupled plasma–mass spectroscopy. USEPA Region 4Google Scholar
- Horowitz AJ (1991) A primer on sediment-trace element chemistry. 2nd edn. LewisGoogle Scholar
- Kiragu GM (2009) Assessment of suspended sediment loadings and their impact on the environmental flows of upper transboundary Mara River, Kenya. Jomo Kenyatta University of Agriculture and Technology, NairobiGoogle Scholar
- Krhoda GO (2006) The hydrology of the Mara River. Mara River catchment basin initiative preliminary phase: project development and stakeholders analysis. WWF-EARPO, NairobiGoogle Scholar
- LVBC, WWF-ESARPO (2010) Assessing reserve flows for the Mara River, Kenya and Tanzania. Lake Victoria Basin Commission of the East African Community, Kisumu, KenyaGoogle Scholar
- LVSC (2008) Catchment management strategy—DRAFT. Government of Kenya, KisumuGoogle Scholar
- McCartney B (2010) Evaluation of water quality and aquatic ecosystem health in the Mara River Basin, East Africa. Florida International University, MiamiGoogle Scholar
- Singler H, McClain ME (2006) A water quality baseline assessment of the Mara River basin. Florida International University, Kenya-TanzaniaGoogle Scholar
- Small IF, Rowan JS, Franks SW (2002) Quantitative sediment fingerprinting using a Bayesian uncertainty estimation framework. In: Structure, function and management implications of fluvial sedimentary systems. IAHS Publ 276. IAHS, Wallingford, pp 443–450Google Scholar
- Sombroek WG, Braun HMH, Van der Pouw BJA (1982) Exploratory soil map and agro-climatic zone map of Kenya. Kenya Soil Survey, NairobiGoogle Scholar
- Terer JK (2005) The study of hydrologic characteristics and management practices in agricultural river catchments: the case of Nyongores River catchment, Mara River basin. Moi University, EldoretGoogle Scholar
- UNESCO (1983) Study of the relationship between sediment transport and water quality. UNESCO Technical Papers in Hydrology, vol 26. UNESCO, ParisGoogle Scholar
- USEPA (1996) SW-846 Method 3052: microwave assisted acid digestion of siliceous and organically based matrices. U.S. Gov. Print Office, WashingtonGoogle Scholar
- USEPA (2007) SW-846 Method 6020A: inductively coupled plasma-mass spectrometry. U.S. Gov. Print Office, WashingtonGoogle Scholar
- Walling DE, Collins AL, Sichingabula HM, Leeks GJL (2003) Use of reconnaissance measurements to establish catchment sediment budgets: a Zambian example. In: DeBoer DH, Froehlich W, Mizuyama T, Pietroniro A (eds) Erosion prediction in ungauged basins: integrating methods and techniques, IAHS Publ 279. IAHS, Wallingford, pp 3–12Google Scholar
- Wolf RE, Denoyer E, Grosser Z (2002) Application note: SW-846 method 6020 for the analysis of soils and sediments by ICP-MSGoogle Scholar