Retention in the riverine catchments: experience of calculation in - - PowerPoint PPT Presentation

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Retention in the riverine catchments: experience of calculation in Latvia

Anete Kubliņa Senior specialist Information Analysis Department Inland Waters Division Latvian Environment, Geology and Meteorology Centre

Uppsala, 19.05.2015.

«Chemical composition of surfaces waters of Latvia and its influencing factors»

• Researches about calculation of retention in riverine catchments are not

deeply developed in Latvia.

• Dr. Ilga Kokorīte in her thesis «Chemical composition of surfaces waters of

Latvia and its influencing factors» (2007) has slightly described theoretically this process and tried to assess retention volumes using a statistical model, but there turned out a variety of problems with the quality of data.

• For calculation of loads nutrients, pollution sources and extents of retention

there was used statistical MESAW model (Grimvall and Stålnacke, 1996).

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«Chemical composition of surfaces waters of Latvia and its influencing factors»

• Calculation of average substances load, using monitoring data;
• Dividing river basin in sub-basins, taking into account placement of monitoring stations;
• Summarizing statistical data about sub-basins (land cover, lake area, loads from point sources or
• ther);
• Calculating of substances load from every sub-basin:

where Li – load from sub-basin i, in estuary (mouth), Lj – load from upstream sub-basin j, Ri,j – substance retention in sub-basin i, n – count of upstream sub-basins for sub-basin i, Si – substances load from diffuse sources in sub-basin i, Pi – load from point sources in sub-basin i, Di – substances deposition from atmosphere in sub-basin i, R1-3 – retention of pollution from sources S, P un D, εi – statistical error coefficient.

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n j i i i i l j j i i

D R P R S R L R L 

The main steps of calculation in MESAW model:

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«Chemical composition of surfaces waters of Latvia and its influencing factors»

Substance retention volumes in all river section till the river mouth is calculated with the formula:

Where R, i mouth – substance retention volumes from sub-basin i till river mouth; K – count of sub-basins; Ri – retention volumes in sub-basins below sub-basin i

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«Chemical composition of surfaces waters of Latvia and its influencing factors»

Results In the doctoral thesis of I.Kokorīte load assessment, using MESAW model, was used for 22 river sub-basins. Model estimated coefficient of nitrogen runoff from agricultural land t-criterion value is 3.5, while from the natural areas it is 3.4. The model estimated ratio of phosphorus runoff from agricultural areas t-criterion value is 1.64, but from natural areas that value is 1.38. There is low statistical significance level for phosphorus loads an retention volumes (p>0,05) (there was not taken into account in calculation soil type, granulometry of soils and topography of catchment basin). Retention of total phosphorus is 22% on average. Retention of total nitrogen is 18% on average.

Assessment of retention in PLC-5 report

• f LV

Retention coefficient for total nitrogen and total phosphorus was calculated, using Behrnedt&Opitz (1998) formula Ntot.: RSN=6.3((Q*86,4*0.365)/As)-0.78 Ptot.: RSN=4,7((Q*86,4*0.365)/As) -0.76 As (area of surface waters in catchment basin) = As=Alake+0.001*A1.185 (Alake (lake area in catchment basin) was calculated, using CORINE Land- cover data) Retention (for total nitrogen, total phosphorus) = RN,P = RSN, SP* Ltot (measured load in river) Results show retention of ~50% on average for both Ntot. and Ptot.

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Mass Balance Model (Version 8.0 - 30/06/2014)

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Data needed:

• Total catchment area, km2
• Mean runoff, mm/year

River retention Lake retention

Thank you for attention!

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