Map 1:
Patterns of European colonization, Counties, and major streams in the URGB.
Table 1:
Historical origins and legal context of URGB irrigation systems.
| Irrigation system traits | Taos acequias | Costilla acequias | Conejos acequias | Anglo systems |
|---|---|---|---|---|
| Earliest irrigation | 1670s | 1850s | 1850s | 1870s |
| Recognition in US law | 1850s | 2000s | 2000s | 1870s |
| De facto water rights in past between systems | Repartimiento | Repartimiento | Repartimiento | Prior appropriation |
| De facto water rights in present between systems | Repartimiento | Prior appropriation | Prior appropriation | Prior appropriation |
| De facto water rights in past within systems | Need and prior use | Need and prior use | Need and prior use | Pro-rata shares |
| De facto water rights in present within systems | Need and prior use | Need and prior use | Pro-rata shares | Pro-rata shares |
| Irrigated land tenure | Vara strips | Vara strips | PLSS | PLSS |
| Sample size | 18 | 12 | 18 | 23 |
The sample contains one acequia in Rio Grande County, but is included within Conejos County for simplicity. Additional descriptive statistics available from the author on request.
Table 2:
Hypotheses, rationales, and supporting literature.
| Hypothesis | Rationale | Key literature |
|---|---|---|
| H1: Hispanic irrigation systems will adopt rules and technologies that promote equality and collective action at higher frequencies than Anglo systems. | Historical selective pressure for cooperative norms drives their internalization, and these norms then drive the adoption of rules and technologies that promote collective action and deter competitive behavior. | Richerson et al. 2002; Nowak 2006; Tucker and Taylor 2007; Prediger et al. 2011; Ghate, et al. 2013; Carballo et al. 2014; Henrich 2014; Talhelm et al. 2014; van der Kooij et al. 2015; Jaeggi et al. 2016; Makowsky and Smaldino, 2016; Gavrilets and Richerson 2017 |
| H2: Where rules are congruent with competitive norms, as with Anglo systems, monitoring agents will reduce water use violations, improve average crop production, and decrease crop production equality. | Internalized norms of competition will amplify the deterrent effect of enforcement, and monitoring agents enforcing competitive rules will generate higher average crop production at the expense of the equality of crop production. | Ostrom 2000; Rustagi et al. 2010; Kinzig et al. 2013; Cody et al. 2015; Rode et al. 2015; Smith et al. 2017; Smith 2018 |
| H3: Where rules are congruent with cooperative norms, as with acequias from Costilla and Taos, monitoring agents will have no effect or a negative effect on water use violations, decrease average crop production, and increase crop production equality. | Internalized norms of cooperation will render the deterrent effect of enforcement negligible or deleterious due to crowding-out, monitoring agents enforcing cooperative rules will generate more equal crop production at the expense of average crop production due to crowding-in. | Ostrom 2000; Rustagi et al. 2010; Falk et al. 2012; Kinzig et al. 2013; Smith 2014; Rode et al. 2015; Turner et al. 2016; Gunda et al. 2018 |
| H4: Where competitive rules are incongruent with cooperative norms, as with acequias from Conejos, monitoring agents will increase water use violations, reduce average crop production, and reduce crop production equality. | Attempts to enforce rules counter to norms will generate conflict as irrigators actively oppose the rules and as monitoring agents fail to effectively enforce water allocations, leading to a breakdown of collective action. | Ostrom 2000; Kamran and Shivakoti 2013; Vollan et al. 2013; Hoogesteger 2015; Rode et al. 2015 |
Table 3:
Variable names, data sources and descriptive statistics.
| Variable name | Data source | Descriptive stats |
|---|---|---|
| Independent variables | ||
| Acequia | OSE; DNR | N: 71 |
| PERCENT ACEQUIA: 67.6 | ||
| Ditch type | OSE; DNR | N: 71 ANGLO: 23 OTHER COLORADO ACEQUIAS: 18 COSTILLA ACEQUIAS: 12 TAOS ACEQUIAS: 18 |
| Monitoring agent | 2013 Survey | N: 71 PERCENT WITH MONITOR: 71.2 |
| Control variables | ||
| Fewer days of water available than normal in 2012 | 2013 Survey | N: 71 Min: −200 Med: −30 Mean: −45.7 Max: 61 SD: 54.5 |
| Days water is normally available | 2013 Survey | N: 71 Min: 15.0 Med: 134.0 Mean: 137.1 Max: 274.0 SD: 68.5 |
| Rotate water delivery in scarcity | 2013 Survey | N: 71 PERCENT ROTATING IN SCARCITY: 76.1 |
| Normally rotate water delivery | 2013 Survey | N: 71 PERCENT NORMALLY ROTATING: 59.2 |
| Labor required | 2013 Survey | N: 71 PERCENT REQUIRE LABOR: 40.8 |
| Inter-system sharing arrangements present | 2013 Survey | N: 71 PERCENT SHARING: 22.5 |
| High capacity groundwater wells present | 2013 Survey | N: 71 PERCENT WITH WELLS: 45.1 |
| Vegetable gardens present | 2013 Survey | N: 71 PERCENT WITH GARDENS: 25.4 |
| Long lots present | 2013 Survey | N: 71 PERCENT LONG LOTS: 31.0 |
| Change water allocations in scarcity | 2013 Survey | N: 71 PERCENT CHANGING ALLOCATIONS: 78.9 |
| Percent Hispanic | 2010 US Census | N: 71 Min: 0.0 Med: 41.8 Mean: 40.5 Max: 100.0 SD: 24.0 |
| Water not allocated by private rights | 2013 Survey | N: 71 PERCENT NOT ALLOCATING BY PRIVATE RIGHTS: 46.5 |
| Dependency ratio | 2010 US Census | N: 71 Min: 0.0 Med: 23.5 Mean: 25.1 Max: 88.9 SD: 12.5 |
| Hold annual meeting | 2013 Survey | N: 71 PERCENT WITH ANNUAL MEETING: 80.3 |
| Percent renters | 2010 US Census | N: 71 Min: 0.0 Med: 17.2 Mean: 17.5 Max: 50.00 SD: 9.6 |
| Percent hydric soils | NRCS | N: 71 Min: 0.0 Med: 17.1 Mean: 18.7 Max: 63.3 SD: 16.1 |
| Average farm area in hectares | OSE; TCA; DNR | N: 69 Min: 0.4 Med: 38.9 Mean: 77.9 Max: 669.9 SD: 121.9 |
| System area in hectares | OSE; TCA; DNR | N: 71 Min: 8.3 Med: 256.3 Mean: 30368 Max: 47475.7 SD: 7850.4 |
| Sprinkler irrigation present | 2013 Survey | N: 71 PERCENT SPRINKLER IRRIGATED: 46.5 |
| Bylaws present | 2013 Survey | N: 71 PERCENT WITH BYLAWS: 67.6 |
| US state | 2013 Survey | N: 71 PERCENT NEW MEXICO: 25.4 |
| Per capita voting present | 2013 Survey | N: 71 PERCENT VOTE PER CAPITA: 78.9 |
| Dependent variables | ||
| Frequency of water use violations | 2013 Survey | N: 71 Never: 31 Less than Once Per Year: 19 Once Per Year: 11 More than Once Per Year: 8 Often: 2 |
| 2011–2014 Average system average NDVI in july | Google Earth Engine; USGS Landsat | N: 71 Min: 0.0859 Med: 0.4499 Mean: 0.4316 Max: 0.6434 SD: 0.1199 |
| 2011–2014 Average system spatial standard deviation of NDVI in july | Google Earth Engine; USGS Landsat | N: 71 Min: 0.0431 Med: 0.2081 Mean: 0.2080 Max: 0.3110 SD: 0.0590 |
The methods used to measure these variables are available from the author on request.
Table 4:
13 features that ought to improve collective action on an irrigation system.
| Feature | Taos acequias (percent) | Costilla acequias (percent) | Conejos acequias (percent) | Anglo systems (percent) |
|---|---|---|---|---|
| No high capacity groundwater wells | 100.0 | 83.3 | 45.4 | 13.0 |
| No sprinklers | 88.9 | 75.0 | 50.0 | 17.4 |
| Per capita voting | 94.4 | 91.7 | 88.9 | 52.2 |
| Labor required for water access | 88.9 | 66.7 | 11.1 | 13.0 |
| Rotational water delivery | 88.9 | 83.3 | 61.1 | 21.7 |
| Water not allocated by private rights | 94.4 | 83.3 | 27.8 | 4.3 |
| Changing water allocations in scarcity | 94.4 | 75.0 | 66.7 | 78.3 |
| Monitoring agent present | 100.0 | 66.7 | 55.6 | 65.2 |
| Annual meeting | 100.0 | 66.7 | 66.7 | 82.6 |
| Long lots present | 100.0 | 33.3 | 0.0 | 0.0 |
| Vegetable gardens present | 88.9 | 16.7 | 0.0 | 0.0 |
| Ongoing inter-system sharing arrangements | 55.6 | 16.7 | 5.6 | 13.0 |
| Bylaws present | 100.0 | 33.3 | 55.6 | 69.6 |
The presence of these features is used to assess the relative preponderance of cooperative norms as opposed to competitive norms. The percentage of each ditch type which possess the trait in question is also given. More information on how and why these variables were selected is available from the author on request.
Figure 1:
Relatedness between irrigation systems based on the features in Table 4. Taos acequias all fall within the same cluster, with some Costilla acequias interspersed. A small cluster of Costilla acequias also emerges, and all but two of the remaining Costilla acequias falls within a third cluster which is two thirds Hispanic. Anglo systems and Conejos acequias make up the vast majority of the final cluster, which has a sub-cluster comprised entirely of acequias.
Figure 2:
PCA shows the relatedness between irrigation systems based on the features in Table 4. Taos remains apart from the other systems, with Costilla acequias being largely distinct from Anglo systems. Conejos acequias range from being more closely aligned with Costilla acequias to nearly identical to Anglo systems.
Figure 3:
Geographic and cultural distribution of cooperation-engendering features from Table 4. The differences between all ditch types are significant (p<0.01).
Figure 4:
Predicted probability of water misuse occurring once per year or more due to an interaction between a monitoring agent and different ditch types. 95% confidence intervals.
Figure 5:
Predicted average NDVI over the study period due to an interaction between a monitoring agent and different ditch types. 95% confidence intervals.
Figure 6:
Predicted average spatial standard deviation of NDVI over the study period due to an interaction between a monitoring agent and different ditch types. 95% confidence intervals.
Table 5:
Results with respect to norms, water rights, and monitoring.
| Ditch type | Norms | Water rights | Monitoring agent | Water use violations | Average crop production | Equality of crop production |
|---|---|---|---|---|---|---|
| Anglo systems | Competitive | Pro-rata shares | Yes | (−) | (+) | (=) |
| No | (+) | (−) | (=) | |||
| Conejos acequias | Cooperative | Pro-rata shares | Yes | (+) | (−) | (=) |
| No | (−) | (+) | (=) | |||
| Costilla & Taos acequias | Cooperative | Need and prior use | Yes | (=) | (−) | (+) |
| No | (=) | (+) | (−) |
The sign in parenthesis indicates the direction of differences observed between systems with a monitoring agent and no agent when compared to the same Ditch Type.