SALINE SEEP 



Situation 



Saline seeps are salty areas that have developed 

 within the last 40 years on nonirrigated cropland. The soil 

 is wet some or all of the time, and salt crusts may result; 

 the salinity can reduce or eliminate crop or grass growth. 

 Saline seeps result from a combination of geological and 

 soil conditions, cropping practices, and to some extent, 

 higher than average annual precipitation. 



Summer fallowing accelerates the rate of saline seep 

 development. It allows the soil to store more water than 

 can be used by the crop in one growing season. This unus- 

 ed water moves down through the soil and permeable 

 subsoils, dissolving the naturally occurring salts enroute. 

 When the salts and water reach an impermeable layer, 

 they move horizontally, and most eventually reach the 

 surface. As the water evaporates, salt deposits are left 

 behind, forming a saline seep. 



The 1978 estimate of Montana drylands affected by 

 saline seep was 200,000 acres and growing at a rate of 10 

 percent a year (SCS 1979). However, careful evaluation of 

 the saline seep mapping project by the Montana Bureau 

 of Mines and Geology and reports by the Triangle Conser- 

 vation District Saline Seep Team suggests that the 200,000 

 acre figure may be too low. 



Seep-affected areas in northern and central Montana 

 appear to be considerably greater than previously 

 estimated; conversely, in southern and eastern Mon- 

 tana the seep areas appeared to be less than 

 previous estimates. On a region wide basis, the 

 acreage of saline seep appears to be expanding at a 

 rate exceeding 10 percent per year. ..Expansion of 

 seep areas by 20 to 200 percent in wet years is not 

 uncommon, whereas expansion of only a few per- 

 cent may occur in dry years (Montana Bureau of 

 Mines and Geology 1979). 



No current statewide acreage estimate of saline seep- 

 affected area in Montana is available. However, the Na- 

 tional Resource Inventory being carried out by the SCS 

 does include an inventory of saline seep acreages for 

 Montana. This information will be available in 1983. Also, 

 several conservation districts have identified saline seep 

 problems in their long-range plans. Teton CD reported 

 10,000 acres are being affected by saline seep, and 

 Stillwater CD reported from 1 5,000 to 20,000 acres are be- 

 ing affected by saline seeps (Teton CD 1 980, Stillwater CD 

 1980). 



Analyses have been made of water collected by the 

 Montana Bureau of Mines and Geology near Fort Benton 

 and Sidney, Montana; Mott, North Dakota; and 

 Lethbridge, Alberta. The resulting data strongly suggested 

 that in addition to the loss of thousands of acres of 

 valuable farmland to saline seeps, mineralized water was 

 rapidly contaminating nearby reservoirs, streams, and 

 shallow aquifers. In some cases, the water was more 

 saline than sea water (water tested was approximately 

 35,000 parts per million total dissolved solids) and was un- 

 fit for domestic, livestock, and irrigation use. Reported 

 livestock and wildlife kills in certain areas may be related 

 to salinity problems (Montana Bureau of Mines and 

 Geology 1979). 



Solving saline seep problems can become a com- 

 plicated landownership problem, which occurs when the 

 area that is the source of excess moisture is under different 

 ownership than the area where the seep surfaces. 

 Cooperation between landowners is often necessary 

 when trying to solve saline seep problems. 



Concerns 



Saline seeps affect Montana's water quality, 

 wildlife resources, soil resources, and rangeland, 

 severely curtailing the yield of crops or taking 

 cropland and rangeland entirely out of produc- 

 tion. 



Objectives 



A) To demonstrate the effectiveness of flexi- 

 ble cropping in controlling saline seep and soil ero- 

 sion, and in achieving water quality improvement. 

 The CD will assist interested CDs to set up four 

 demonstration plots in Montana. See Part A, Ob- 

 jective 19 of the Work Plan. 



Rationale: Farmers have been reluctant to 

 use a flexible cropping system to control saline 

 seep. Demonstration plots will help educate 

 agriculturalists on the use of flexible cropping 

 systems. 



B) To make more assistance available in 

 saline seep prevention and control. The CDD will 

 request the SCS to provide more trained technical 



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